Some people might choose their place to stay based on availability of night life and some other might avoid certain area because of the same thing. Probably the latter group is more likely than the former in the case making decision based on clubbing/night life scene in the area.
KLCC is high class for high income but it has very little to do with the availability (or lack of if you prefer) of a clubbing scene. As for the clubbing crowd in KLCC I thought it was a well known fact that the majority there is not locals (and that's even when excluding the foreign tourists) and that's the way it has been for at least the last couple of years. Hint: go to KLCC LRT station at any Friday/Saturday after 7pm and see who arrives and who leaves

Why would a company choose to pay higher office rent in KLCC (for example twin towers) compared with other office locations?
Because of the smooth KLCC traffic? Nahh, jammed.
Because of LRT station? I don't think so, got plenty of cheaper office locations along the LRT lines.
Because of great places to have lunch? Because of good shopping malls nearby?
Because it's KLCC and in Malaysia KLCC is associated with class. You know you want that KLCC address on your business card.
As for the TRX we'll have to wait and see how that develops, just because the gov't have some ideas about what kind of development they want there doesn't mean it will happen (e.g. Cyberjaya).
Cant say it better myself.