I don't know why the long warm ups are needed, but I'm in the same boat.

If I ride for an hour, 40 minutes of it are spent warming up . . . but I get a great 20 minutes high intensity ride.

I need to warm up for an hour before I play a tennis match. When I run, I need to walk for 20 minutes otherwise I get shin splints. I used to fight it and always tried to rush it, but ended up with injuries and frustrations. Now, I just accept it and try to give myself more time.