Comment by wiether

Part of my job is to do migrations for customers, so, to me at least, it's not uncommon.

Using all the bells and whistles of a provider and being locked-in is one thing. But the other big issue is that, as service providers, they can (and some of them did more often than not) stop providing some services or changing them in a way that forces you to make big changes in your app to keep it running on this service.

Whereas, if you build your app in a agnostic way, they can stop or change what they want, you either don't rely on those services heavily enough for the changes required to be huge, or you can just deploy elsewhere, with another flavor of the same service.

Let's say you have a legacy Java app that works only with a library that is not maintained. If you don't want to bear the cost of rewriting with a new and maintained library, you can keep the app running, knowing the risks and taking the necessary steps to protect you against it.

Whereas if your app relies heavily on DynamoDB's API and they decide to drop the service completely, the only way to keep the app running is to rewrite everything for a similar service, or to find a service relying on the same API elsewhere.