If we’re discussing major corporations, they are willing to pay a premium for predictability and reliability of service. Cloud vendors provide just that: if you want more resources, you can scale up until you hit capacity, then you can call the account manager to increase it. Very little downtime (except for the occasional outages). All of these are known processes.

With operating your own DC, you have to hire really great people and hope they don’t fuck up. You have to plan much in advance for capacity changes. It’s very much possible that something goes wrong in your compute infrastructure and simply nobody in your team has the expertise to fix it. Put it another way: can you pay/hire the same kinds of engineers that work at AWS/GCP? If not, cloud is the safer route. Cost does matter, and this is why companies sign multi year contracts to get discounts. But business continuity is critical.