Finer tuned accuracy. Curling is genuinely super fucking hard, part of the reason so many pro curlers are fairly old is partially cause it isnt that physically demanding so you can keep it up at an older age, but also cause it just takes that long to get really good. It would prevent rhe rock from spinning or allow tou to slow the spin after releasing a bit more than you coukd using the handle, or curling which can be useful at certain times. I am weird and the only sport I care about is curling. Little boops translate to a big difference over a long distance.