No more responses???
Why is e4 so commonly played in the first move?

e4 is actually not the best by test, d4 has a slightly higher win rate than e4. Also a slightly lower loss rate as well.
1-It gains space in the center.
2-It (kinda) discourages Black to play 1...Nf6
3-It frees the LSB
4-It frees the Queen to attack via h4 in some variations
5-It is the most macho first move
I think I covered most of them.

Yes, but nobody has actually answered my question yet with a convincing reason. Why not nf3 or nc3 or d4 or b3 or g3?

Why is e4 so common? Why not nf3 or d4? They are played, but not so commonly. Why?
That is absolutely absurd to say d4 and Nf3 are not commonly played.
For example, on 365chess.com, a far smaller database than the mega base that you can buy, 1.d4 is played literally over a million times!

Yes, but nobody has actually answered my question yet with a convincing reason. Why not nf3 or nc3 or d4 or b3 or g3?
And 1.Nc3, b3, and g3 are all a step below c4, d4, e4, and Nf3.

Well, I prefer 1. d4 but let me explain something:
1. Both 1. e4 and 1. d4 avoid transposition.
2. 1. e4 open up more line to attack (open the d1-h5 diagonal for the queen, f1-a6 diagonal for the bishop => attack best, and so we have the Scholar Mate, YAY!!!)
3. 1. e4 controls d5 and f5 (I personally don't think 1... d5 a.k.a the Scandinavian is balanced since after 2. exd5 Qxd5 3. Nc3, White has quite significant development advantage, sideline is 2... Nf6, in which all White need is to give up the d5 pawn and enjoy developing)
3-: 1. d4 controls e5 and c5, but 1... e5 (Englund Gambit), and 1... c5 (Old Benoni Defense) has traps, and thus, Black dare to play such move.
4: Other than 1. e4 and 1. d4 doesn't seems great: 1. Nf3 is defensive-looking, and 1. c4 only opens up the d1-a4 diagonal, and if Black plays normally, then this doesn't seems to be a benefit. It controls d5 and b5, but Black can just goes for 1... e5, then it seems Black is more active. And... other moves don't deserve explanation.
(But after 1. Nf3, Black would normally play 1... d5, in which White can set up the notorious Tennison Gambit)

Well, I prefer 1. d4 but let me explain something:
1. Both 1. e4 and 1. d4 avoid transposition.
2. 1. e4 open up more line to attack (open the d1-h5 diagonal for the queen, f1-a6 diagonal for the bishop => attack best, and so we have the Scholar Mate, YAY!!!)
3. 1. e4 controls d5 and f5 (I personally don't think 1... d5 a.k.a the Scandinavian is balanced since after 2. exd5 Qxd5 3. Nc3, White has quite significant development advantage, sideline is 2... Nf6, in which all White need is to give up the d5 pawn and enjoy developing)
3-: 1. d4 controls e5 and c5, but 1... e5 (Englund Gambit), and 1... c5 (Old Benoni Defense) has traps, and thus, Black dare to play such move.
4: Other than 1. e4 and 1. d4 doesn't seems great: 1. Nf3 is defensive-looking, and 1. c4 only opens up the d1-a4 diagonal, and if Black plays normally, then this doesn't seems to be a benefit. It controls d5 and b5, but Black can just goes for 1... e5, then it seems Black is more active. And... other moves don't deserve explanation.
(But after 1. Nf3, Black would normally play 1... d5, in which White can set up the notorious Tennison Gambit)
Right
OK, the main reason e4 is played so often is that you can castle in 4 moves AND not relinquish any control of the center. For example 1.Nf3 can also potentially castle in 4, but white lacks a bit at the center fight since black can play 1...d5 and white needs to do a few more moves before castling.
Thus, e4 allows you to develop a knight and a bishop very fast, castle also very fast and then be able to complete development and get on with the game. This is especially important for beginners who most of the time lose because they lagged behind in development.

When new players start playing chess, they are recommended by most people to play e4, people don't like to change their habits, so when they improve, they will stick with e4. Interestingly, according the chess.com database, there are about 2.7 million games. less than half of them start with e4. e4 is the most common move however over 50% of the time, someone will start with something else.
Pawn masters