ISI is a small team and they probably have priorities elsewhere than to get support for some developer product. It's a nice PR move to support it but it won't have any impact for 99% of users, so why waste time on implementing support for different dev versions if it can be implemented once, for the final consumer product.
Small team or not it doesn't matter really TBH. There are bearly big simracing dev teams.
With the rift you can hook up users as it showcases rF2 really good and with the rift you obviously spend more time with the sim than just 10 laps. Also most people with the Occulus Rift in the simracing scene are more or less die hard simracers, so it wouldn't be a bad move to get those folks onboard. I do not belive it is a hard task to intergrate it anyways.
I don't see it as a waste of time at all, actually at this moment I can't see the time better spent. Later on when every body has it....well yeah rF2 users might get the kiss too. The DK2 doesn't differ from the CV version regarding implementation at all, that was said by the Oculus team. But yeah, who the hell cares. Don't implement it at all, it is a waste of time anyways like all the peole talking about it, buying it, spending time with it, it is all a waste of time anyways.
I am not sure you got that percentage number right tho.
EDIT:
Sounds a bit frustrated maybe. But it made me frustrated really. I even had an iRacing race lol yesterday which would have never possible without their rift implementation. And I bought Spa just to compare it to AC. They have improved a lot but still the FFB on the limit is useless. I have spent the majority of my simracing time in AC since I have the rift and that isn't either my sim to go.
It is just rF2 where you shall not have it because whatever. The time spent now would effectivly have been better on the implementation than later on I belive. If the new UI is some sort of hurdle I don't know.
It is indeed frustrating but I'll cool down eventually again lol.