In prefix notation (which has been around for a very long time) the operation comes first. Think of it as the "addition" function being applied to the arguments following it. This matches how nearly all programming languages are broken down into their abstract syntax trees while compiling.
As an added bonus, you now know Lisp. This is how all Lisp syntax works: `(function arg1 arg2 ...)`. That's literally it.
"Typical convention" is also an Appeal to Tradition. Different traditions though!
Incidentally, people used to be /really/ against Python because of its use of significant whitespace. The number of people who bounced off it because they would try to type something and then get a mysterious syntax error that turned out to be that they didn't type space or tab the right amount of times! It used to be what people would immediately post whenever anyone said anything about Python.
I think now people get introduced to IDEs at the same time as Python, or something happens at that early teaching moment that gets them over that hump. The same, in theory at least, happens when you play with a lisp long enough.
As an added bonus, you now know Lisp. This is how all Lisp syntax works: `(function arg1 arg2 ...)`. That's literally it.