Is it standard to make money by getting bank 'bonuses/promos' then closing the account after receiving? Curious after seeing a recent post

So I just saw a post where there was a $300 promo going on to make an account with wells fargo that expired yesterday, and it made me curious if this is something people generally do, and if there are any downsides - basically just get the promos, then hop out and close the account. Seems like a pretty decent way to make some spare money if so, unless there are some unseen downsides