The problem with solid spoked wheels on tractors with just rubber added to the wheel is the total lack of suspension in most tractors. The tractor would be severely limited in operating speed and the operator would be severely limited in the time he could operate the equipment without being bounced to death inside the cab. I wouldn’t relish the thought of having to wear a mouthpiece and helmet, just to do a little landscaping.
In the case of a car, it would put a lot of demand on the suspension system.