Why is e4 so commonly played in the first move?

yeah, good point

thank you!

OK, I guess I should wait for others to give their opinion because it is only a few people replying anyway.

yes.

dude, just go to stockfish, and it will say e4 is best initially. It will then consider d4 and c4, and then it will find out that Nf3 is the best. Nf3 is indeed the best, but e4 is almost as good, and can be used by low level players. If one 800 mastered the Reti and all of its variations, and they could play a decent middle and endgame, they would spike more or less 300 - 400 points. The reason that it doesn't happen is you need to master everything in it. That is too much work for casual players. That includes me, but I am fine with e4. Just study some openings, and if you find one that you really work well with, then play it and you'll win a lot of rating. Just know how to beat those pesky defenses (Sicilian, Caro-Kann, French, etc.).

Chess engines are most accurate in middlegames and (depending on the engine) endgames. From a human perspective there isn't much difference between d4, e4 and Nf3 in terms of chances for white.

yes, pilotoxomxd, i completely agree with you and your opinion. good point!!!

true!!!

but i agree with pilotoxomxd that it takes loads of time to master other openings like the reti or the london system. i also find playing against the sicillian opening very irritating as i am not used to it.

The Sicilian is a big problem for e4 players as it gives black a very good chance to seize the initiative. Against d4 black's best try is the Gruenfeld defence if he wants to gain the initiative.   

is the alapin variation good to counter the sicillian?

Short answer yes, as it can annoy a Sicillian player as it will go against their style of play, however I've found that going for an open Sicilian is the best and most fun way to play.

ok, but you may be accustomed to playing the sicillian but i am not.so i find it tough to play, so what to do?

Never played it. I usually play Closed Sicilian or Prins variation as white.

most people learn e4 first, so they stick with it

ok.

yup

Also, Smith-Morra gambit looks like a fun way to play.

But I changed my opening to d4 even when I did e4 first or b3/g3 first

Try to play a closed Sicilian. Most beginners are used to open Sicilians, and playing