Don't see a reason for fuel cost myself, I only get one and by adding a fuel cost you narrow potential OKW openings, since one day, much surprise such wow, people might actually WANT to play non meta with Kubel spam.
TLDR: Fuel cost reduces fun openings and keeps OKW volks spamming.
As do I, even in this patch, probably because they don't rely on Churchill cheese (got a cast of me and a friend on ATR's channel where we are losing but Churchill spam brings us back). Whilst it's a slightly odd faction now and they hobble along somewhat geriatricly I enjoy playing them since they are very much allied Ostheer.
Shame their free commanders are bad/bugged/nerfed because Royal artillery is really fun to play. If I had Special Weapons I'd play it all the time.