You don't have to pay cloud providers. You can rent a dedicated service from a hosting provider and go to town with it (very much limited by your bandwidth or transfer limit).
Cloud providers are used because there is a lot of vested interest - e.g. VC and investors also having shares in cloud companies, then there is fear their investment might not survive imaginary surge of traffic that will never happen in reality. Cloud sales people are masters of playing at investors insecurities.
I think it’s also largely driven by the apparently cheapness of turning the CapEX of server buying to the OpEX of cloud renting. Less up front investment and auditing/access controls for SoC2 compliant are so much easier m.
Cloud providers are used because there is a lot of vested interest - e.g. VC and investors also having shares in cloud companies, then there is fear their investment might not survive imaginary surge of traffic that will never happen in reality. Cloud sales people are masters of playing at investors insecurities.