It really depends on the product, company, and possible regulations.
If it's 'just' a restaurant website that has a bit dynamic content, and you can make reservations. I think it's much better not to build/host your 'own' backend, but just use services. If you have a payment platform, and it needs to be cost efficient and to apply to a lot of regulations, you need your 'own' backend, and you need to think hard about the services you use.
The "build or buy?" question would be the next step, I think.
But you made good points to that question!
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