I've long been an advocate of sin bins. I use them now unofficially with my mini footballers.
an example of where a sin bin would be appropriate- a team breaks inside their own half they have a numerical advantage, attackers over defenders, a player on the now defending team stops the move developing with a deliberate foul. Currently its always a yellow card as its a long way from goal and the attack hasn't fully developed, but a clear advantage existed to the counter attacking team. imho a yellow card isn't sufficient, it provides no redress to the fouled team, but a red card would be harsh. The defending player is always happy to commit the foul and get carded "taking one for the team".
If it meant 10 minutes in the bin, I think it would be very different. There are many other scenarios where a sin bin would be an effective deterrent, time wasting and simulation as examples.
a talented kid I coach at grass roots under 10s is in his local ADC, one step down from full academy.
Wednesday he trains grassroots, Friday he trains ADC, Saturday plays grassroots and Sunday occasionally plays rugby at grass roots level. he's a decent rugby player, he can already place kick and drop kick over adults posts from the 22.
The amount he can play rugby is limited because the ADC sometimes arrange matches for Sunday including full academy trials. It seems obvious to me that these take precedence over grass roots rugby. However his grass roots rugby club take a different view and say unless he commits to most Sundays they wont play him and suggest he gives up rugby. eg he can play rugby this Sunday in a tournament but they've told him not to come.
If he was in the full academy he would not be allowed to play grass roots anything.
As a grass roots football coach I can sort of understand them needing commitment from kids, but equally if a 9 year old turns up with a pair of boots for a grass roots game of rugby on a Sunday I think he should be allowed to play.