My limited read of the history of the wheel is that it was first used as a weapon of war. Why would it be different than any other first use of technology.
My observation is that the wheel was first introduced in the use of war chariots.
In my thoughts it is an obvious first use. In chariots the loads are relatively small; two men and their weapons.
Horses also were mostly used as weapons because you had to rich to afford to keep horses.
Put the horse and the chariot together and you have a formidable weapon.
These are my own observations so I would appreciate your more informed opinions.
To me, the proto/early-human who gets the "genius award" is the one who first used something softer than flint for a hammer -- because its control opened up a whole world of advanced tool development.
Heck, when I was a kid, we had "long range mudball wars" -- using springy willow sticks to give us 100+ yard range. But, we never got the notion to throw a lightweight spear ("dart") with them -- ("Atlatl")...
TXnMA