Earlier quoted context omitted.
These tend to be early stage startups who went with BaaS to get around resource constraints and couldn't survive the rapid need to exfiltrate their data and build a backend with a gun to their head. Larger companies generally have the survival sense not to sharecrop business critical functionality to such a degree. Which is to say, you wouldn't have heard of them, because they never got big enough to be known to anyo…
Do you consider AWS Lambda and such to be BaaS? I'm pretty new to the field and have been focusing on AWS 'serverless' as the backend for most projects. Would you say this is bad practice overall?
The objection here isn't to hosting per-se – most companies aren't in the business of maintaining PostgreSQL and should consider outsourcing that task early on. If your host of choice shuts down, that's a standard service, you can dump and restore your DB and move on. Annoying but NBD.
The danger with jamstack or BaaS or similar approaches is working yourself into a place where a proprietary service API is baked into your product as a critical, fundamental dependency; if and when the host shuts down, you're in extreme trouble. That's what I'd heavily caution against.
(There's an argument that when the proprietary service is run by an MS or AWS or Google "they won't go bankrupt" so there's no risk, but even then those companies shift priorities and shut down services not infrequently).