So what are the reason Nadeo does not fix them?
TIME!
Nadeo has no endless capacities. They are a relatively small team of developers.
Their current priorities are the development of shootmania and Maniaplanet 2.0 (and valley afterwards, I guess).
And because nobody wants to wait long for the new stuff, Nadeo uses all their power on this new stuff to finish it as fast as possible. (They also gain more money with the new stuff, but this is a different reason

If they started to fix the problems in TMUF/TMNF, it would slow down the process of developing SM and MP 2.0 and the new stuff. Then we would have to wait longer for the new things and many people would flame about the release dates.
To keep it simple: Nadeo use 100% of their energy to bring SM and MP2.0 fast enough, so that there is 0% of their energy for other stuff left. got it? :p
Even this discussion costs some time

EDIT: I am happy with the current situation of TM, as I see and except it how it is. I still have FUN!