a. because the tweeters in the door are crap and it costs £200 per door or something like that to get at them out
b. they are placed in the wrong position which is partly why the sound is crap since you get a mishmash of sound coming from the rears at ear level as well as the front
c. the is no crossover in the tweeters so you'd have to replace them in any case if you like them at that position and get proper ones with crossovers, with the cost of taking the door apart unless you are an expert at taking the door apart yourself [that's the Altea cost above]
So best to disconnect them and be done with it, which is what the Altea folks did years ago, for the last two years. Obviously you can hand over a mint to someone but part of the enjoyment is doing it yourself.
The disconnection of the tweaters, the speaker mountain etc was something that was worked up as a solution. The other thing is that people want to move the speakers with them as they change cars hence they have no desire to get into heavy work and costs, they have a rep car, want to hand it back as they got it and take the speakers with them, that has come up a lot as well, least in the Altea area.
This thread was spawned since New Leon owners took the Altea solution that I posted up in mid 2005 and started using it themselves on Leons, I didn't tell them too, I just got told by one of the Altea owners when someone bought the wrong speakers and they got poked in the eye when they tried to be
help over here and said take a look.