A low percentage of goals have an infraction with a chance of getting the goal (given by the ref) disallowed. And maybe only give each team one challenge, so they don't waste it. It's better than having the other team celebrate a goal that shouldn't have been given.
Yes that's more tricky. There...
With cricket, as you say, the umpire can check for run outs. There would have to be a strict limit on things a football ref could check for. Team captains and managers could also check other things, but they'd use up a limit of challenges.
:lol:
I can picture a defence lawyer clutching at straws while their client faces assault charges - "He was just caught in between some people and tried to untangle his fists".
If you're legs are tangled, you roll away and your legs, miraculously, come with you. You don't kick.
What's more...