Also a small scout spare shouldn't be able to use for a heavy truck to repair.
Well, for my ~100 hours in game I've used spare wheels only to repair trucks, which were required for missions (fix it, fuel it and tow it back to garage). And how many missions of this kind in this game? Something about 5ish?
In any other scenario it's very, very hard to break wheels if you not trying to do it on purpose.
And if devs will follow your suggestion, this feature will become even more useless than it is now, as it will limit it's usage by adding scout/truck tires differentiation.
They should rebalance it somehow. Don't know how exactly they should do it, but one of the possible solutions is to make wheels easier to break for example, but wouldn't it be rather annoying feature?