Because if you move randomly, then every time you're playing someone, you'll run into this.
Lol, there might a difference between "randon" and moving intelligently.
I'm a newbie myself, but have been told that it's better to open according to the simple opening maxims, rather than learn specific openings. i.e. Move once, control the center, develop your knights before your bishops etc.
I guess it would be pretty pointless learning a specific opening if you're then stuck with what to do when your book knowledge runs out. 
I mean there are plenty of reasons. Although its not necessary, natural moves can sometimes get you into trouble:
That works well at the 1600 and below level, for sure. Often you'll see some really bad development there, though, such as way too many pawn/Queen moves at the outset. Normal development rules should knock over players like that quickly.
But in terms of actually knowing openings, it becomes useful at the level at which most of your opponents know them too. This will vary. When you find yourself getting thrashed just because of a bad or inaccurate opening move, it's probably time to do a bit of opening research.
And as for book knowledge running out - well, we haven't mapped out the whole game just yet, so your opening knowledge will run out eventually. Knowing openings is really useful in 1) getting to positions you like to play in or are comfortable with, and 2) not getting ruined in the opening, being able to reach equality by middlegame.
Steev, you're right of course.
I should have prefaced my post with saying "at my level" 
p.s. My "lol" was at the random opening in your example, not your post.
I geuss i was t hinking at my level,but as trant said earlier i would just start developing and controling the center but of course steeve is right in a way.sometimes i do get into that kind of trouble.maybe i am bad because of a bad opening and bad middlegame based on bad opening.
I think the advantages to learning an opening at any level are...
1. It will save you time on the clock OTB to play an opening line you've seen 1,000 times, rather than have to think each move out.
2. You will consistently find yourself in familiar positions that you like, with themes that you know how to exploit.
3. You will have your pieces developed to active squares.
Sure you could do this on your own. But more than likely, you would be playing an established opening line anyway, so you may as well know what it is, and not reinvent the wheel every time you play.
but why cant u just reply to the other opening's moves?as for being comfortable with the position of the opening isnt it fun to play a different game every time?and why do u need to rush?isnt chess all about thinking?cant u think each move out?
but why cant u just reply to the other opening's moves?as for being comfortable with the position of the opening isnt it fun to play a different game every time?and why do u need to rush?isnt chess all about thinking?cant u think each move out?
You dont play in chess tournaments do you ?
no not really
Well, ofcourse not all the different types of chess players need to learn openings nor to " rush " their moves. Their needs are not the same, their goals are not the same. A casual player who only plays a few games a year with family or friends certainly doesnt need to learn any chess theory, but someone who plays serious tournament chess and is really trying to get good in chess does.
but why cant u just reply to the other opening's moves?as for being comfortable with the position of the opening isnt it fun to play a different game every time?and why do u need to rush?isnt chess all about thinking?cant u think each move out?
Yes, but that takes time. If you know them, you can use that time to think more deeply at other moments of the game. If your opponent doesn't know them, he's at a disadvantage.
But at your level, you don't need to know them.
You're not bad because of your bad middlegame or opening, you're bad because you don't seem to think about your opponent's next moves at all. You need to start checking whether your opponent can take one of your pieces for free on the next move, or checkmate you. That's where it starts.
alright but why canat u think deeply on all the moves including the starting ones?
If we didn't use a clock, that (thinking deeply from move 1) wouldn't be an issue ... but if you take 30 minutes for your first 8 moves and I take 4 minutes, you're in trouble on the clock.
There are only three choices, really: a) if you're serious about traditional chess, you must eventually learn real openings, b) if you're strictly casual about it, you can take it or leave it, and c) play Chess960 (well, not a panacea, but essentially eliminates the memorized lines issue and raises the value of ideas, themes, and sheer calculation in the opening phase).
but we have time for 30 min right?the lowest on chess is 1 day.i always do 1 day and think for a while and i get along just fine with the clock
Well, you have a point IF the only kind of chess you will play is correspondence, then have to have opening lines memorized is not an issue AT ALL. In correspondence (i.e., Online chess here at chess.com), you can use opening manuals during your game. So, it's really not an issue at all. But that is certainly not the primary form of chess played in the chess universe.
I was speaking about OTB (over-the-board) chess and Live Chess. Sorry if I did not understand that you were referring ONLY to Online/correspondence.
Well I don't and consider it a point of honour not to :-)
wat is otb? and for live chess i agree
Why do we need to learn them?Why were they even named?Why do we need them?I am not the kind of person who would start naming and learning openings.Why do we need to have them?Why can't we just move out our pieces randomly how we think is best?
wanna see some opinions:)