Why do we need it?

If you thought hard about each move, and were a good chess player, you would eventually just play the named openings anyway. So, we have documented them to avoid all this arduous thinking time that we could be devoting to having a life.

wat is over the board?

Real-life. Non-computer.

why not? my dad wouldnt care if i thougth for a while

"Why can't we just move out our pieces randomly how we think is best?"

You are welcome to do that and you should. Given enough time and experience you will no doubt develop a list of opening moves and their performance statistics and it will probably help if you give your variations nomenclature for quick and easy reference. It is a tried and proven method commonly referred to as "re-inventing the wheel".

In proper OTB play you are on a timer.

Whether you know it or not, all of your moves follow from your strategy. That is, when you move a piece or pawn you want to accomplish something: i.e. move king's pawn to 1.e4 to take a stake in the center of the board and allow the king's bishop room to move to a position where it can take place in the battle to come. Along similar lines, you may move your queen out early, attacking black's f7, hoping he'll fall for scholar's (or fools) mate; i.e. White e2-e4, Bc4, Qf3, mate with Qxf7. Now is this a good strategy or a bad one. If you're playing against someone who doesn't know the game. you'll get some wins, so the strategy works. As you play better players they anticipate an attack on f7 (or f2), like a street fighter expects a kick in the groin. It won't work. Is it bad? Well good players will take advantage of your early movement of your queen to attack her while developing on of her pieces. You'll fall behind indevelopment of your pieces and so the strategy is a bad one. So you have to learn a new strategy if you are going to beat stronger players. Just like with a general commanding an army or a coach a football team, you don't just say "go out and do your best, or do whatever looks good to you at the time." You learn opening principles for the same reason coaches develop plays and armies learn maneuvers. So it's up to you. If you want to be a good player you have to learn the fundamentals. If not, then just go out and play and no one else is going to care if you impove or not. It's up to you; it's your move!

The point of the opening is to get to a playable middle game.

You can do that without studying openings but it's a lot harder and eventually if you get serious all you will have done is recreate the work of others who have gone before you.