I'm pretty sure that if Toei decided to incorporate Kuuga-like bike stunts into KR again, it would cost a hell of alot more money. They'd probably have to take some of the CGI budget or something and use it. Tominaga didn't do the bike stunts in Kuuga, they had specific stunt bikers for them. Not to mention probably alot more bikes, because I'm pretty sure the TryChaser broke down a couple times during shooting.
Kuuga probably had a larger budget because it was the first series in awhile, and thus could probably spend more money on bike stunts.