Almost all pros in the top 20 have key points in there stroke collection. Certain little aspects that a biomechanics coach can identify. Without these keys the players strokes would break down become erratic. Then they would be low level players suddenly.
Coaching does not have to be too analytical in that respect. Its use should be to try and let players develop there own natural styles and game.
The problem is that most people don't pick these key points up by them selves and usually need coaching to learn them. Coaching is just an aid to learning.
So of course you don't need coaching ... but its there if you want it.