Maybe its the other way around... because the game was in prodution before they add any info on the wheel, and they cant guess what technology is coming out and program the game accordingly.
You have to be fair besides GT5 there is no other game for the PS3 that supports the wheel not even TDU2.
Its a great wheel but its a new technology (h.e.a.r.t.) and there wont be any games that support it for the PS3 in the next few months (maybe summer releases will suport it)