I use it b/c some vendors accept btc, and they do an easy payment option. The discount for using btc outweighs the fees.

It's because it's a great place to HODL for me, since they seem vastly more secure than all the sites that have gone down in thievery and flames over the years.

I think it'd be disingenuous to suggest that there is any safer place to hold crypto, given they are publicly traded, have excellent engineers, have insurance, etc. I even think it's more likely I'd fuck up personally custodying my crypto than letting Coinbase hold it. I've had friends lose so much money trying to keep their crypto in private wallets and on shady exchanges.