The “why” goes a little further than that.

In actuality, it’s because of fundamental properties of operations

• Commutation

a + b = b + a

a×b = b×a

• Association

(a + b) + c = a + (b + c)

(a×b)×c = a×(b×c)

• Identity

a + 0 = a

a×1 = a

If you know that, then PEMDAS and such are useless because they’re derived from those properties but do not fully encompass them.