Lots of you are missing some basic point in the differences

Lets say your chain, BB, crank, RD, FD, and cassette were all self lubricated AND enclosed within a aluminum casing.
Now lets say your wheels (hubs & axles) were sealed from the elements and lubricated.
Then lets say instead of mounting to a dropout/hanger, your RD is a very robust thing that never moves - only the internal parts move. And the internal parts move in a very different way than a RD.

Now how much less maintenance would you need to do...
That's why a car can go 3-10,000 miles between any maintenance - its systems are protected from the outside world and always lubricated properly. The design on the transmission is very different than a bike's transmission.