Apple could spend millions on developing the perfect mouse. And as demonstrated here and virtually everywhere, there is no such thing as, "just right."
Glove, hats and shoes are the most difficult to buy. Too many variables. Too many functions. Too many sizes to choose from. Same for mice.
And as the adage goes, 'the more choices one has, the longer it takes to make a decision.'
As I have said before, I can walk into any computer lab or clients offices, invariably I won't find two users with the same mouse. And now, I have clients that are telling there employees and even teachers to keep your mouse to yourself because of the flu issues.
In the near thirty years on Mac, I can't remember the last time I every picked up and felt comfortable using a client's/colleague's/student's/friend's mouse. And they have expressed the same as well.
Like my car, boat, entertainment system or sports equipment, there are many things and accessories that just fit/work/look better than offered from the original manufacturer.
For one thing, Logitech, MacAlly, Microsoft, etc., make some great mice. Thank heavens they do because they haven't made a great computer or OS to shove it into ours faces.