Your obviously is only a convention

Nope. Rules of Maths

it would have to have different order or parentheses or both.

Neither. Multiplication is always before Addition, hence "obviously"

Of course everything in math is convention

Nope. The vast majority of it is proven rules

2+(2*4) is more obvious to common people

Weird then how many people were able to get this right without brackets for centuries before we started using brackets in Maths (which we've only had for 300 years)