why do some sportsbooks allow betting after games start

Was checking lines and noticed a few books let you bet even after the game’s started. My first thought is that it’s a way for them to keep action going, but it gets confusing with how fast odds change. I stick to table games more, but with sports it’s wild how you can put money down while the score’s already shifting.

Curious how folks use it without just guessing - feels like you’d need lightning fast reflexes or just stay super steady with your bets. Seems like a big risk if you’re not careful.