I think the answer is that the teams are too
Ie smaller teams want some things & bigger teams want something for giving up some things.
This lil snippet is from the press conf @ Sepang on Fri,3/19 to Tony Purnell (Jag/s Director):
<b>Q: (Tony Dodgins - Motorsport News): One of the problems with split qualifying unlike last year is that the drivers only donít take a risk in the first session. Now one of the ways to get around that would be to aggregate the two sessions, but a team principal said to me this morning that that was dismissed because the engine manufacturers on a one engine per weekend situation didnít want to be faced with having to run higher revving one lap engines. Is that valid?
TP: I think thatís dismissed because the aggregate system is going to put more variability in it. That doesnít favour the strong teams so theyíre going to reject it, which is in their interest to do. </b>