I found a working (but empty) RV sitting in front of a gas station once, I promptly drove off in it (after dragging a broken motorcycle over to a gas pump, filling it, and then dragging it over to the RV to siphon gas), but I’ve never again gotten that lucky finding a vehicle on day 1.
Also even if you are tailored for repairing vehicles you probably won’t find a welder, a wrench, a hacksaw, and a decent vehicle missing parts you can scavenge from the local vicinity in time to repair a vehicle on day 1, unless you happen to forego collecting other supplies (like food, water, and carrying capacity).
I agree with game balance in theory, but practically cars shouldn’t be rare or hard to get, they should just be limited in how useful they are.
Carrying stuff long distances on paved roads is what they’re really made for, not driving offroad through hundreds of zombies, shrubs, giant mosquitoes, and small trees. A good reinforced vehicle should probably require finding an abandoned military vehicle or DIY, which balances out the difficulty and effectiveness pretty well, though pure random chance can still play its role.