If it's still book that I know I don't use "2-5 minutes" but I do take some time to make sure I'm remembering it correctly and check to see if I remember my opponent's different responses that I'd planned for. This also helps keep the pace of my play slower like schachgeek was saying.
I've spent time on my 2nd move before though. Playing someone rated about 500 points higher I was white and after 1.e4 c5 I thought for 1-2 minutes if I wanted an open Sicilian or a closed one.
I don't understand why they waste time on their first move.
It's not a waste of time if it helps them clarify exactly what they are going to play. It's all very well to have openings planned etc but sometimes in the heat of the moment when players sit at the table they actually do something different so it's worthwhile having a think for a few minutes just to get everything levelled out in your head. 
ok, I thought I was clever by planning everything in advance.
but if a 2500 rated player suggest something I listen. Maybe I could slow down a little.
usually I play my first move in under 5 seconds almost as a reflex action to my opponents move. Maybe I should wait 1 minut just to slow the game down with my opening knowledge right now it is doubtful that I am going to play something else than I would have else.
maybe it made more sense if I knew more openings and the theory behind them.
Yes it is stupid to waste time on the first moves like that. Some think that it has some "psychological effect" on their opponent but that's alot of bull imo and if you haven't decided what to play to the first move like 1.e4 you're doing it wrong.
People spend a lot of time on move 1 only when they expected something else and have a broad repertoire. For instance, someone has spent the whole night refreshing his preparation in the KID, and then he gets 1.e4 instead of d4! That may be a shock, so people take their time to recover from it, try to guess what the opponent has prepared, and deviate.
when I enter tournament in real life.
I have seen a lot of people who waste 2 or even up to 5 minutes on their first move. if I play e4.
I don't understand why they waste time on their first move. I know you have to sit on your hand and not play to fast in tournaments, but on the first move?!
Personally I know before the game what I will play if my opponent plays e4, d4, c4 or even any other move. No need to waste time.
does it make any sense to think about the first move?
can't you just plan the first 2 move moves deep at home before the game no matter what is played? - at home you have all the time in world.