because saying your business is built for and in the cloud gets you investors and street cred. further, if you are having a bad quarter, you can squeeze your in

because saying your business is built for and in the cloud gets you investors and street cred. further, if you are having a bad quarter, you can squeeze your infra to lower opex. If you built all onprem, you had to invest capex heavily upfront, and you can't slow down your opex very much in the bad times.