Really, you could make the argument for any AWS service and generally using a cloud service provider. You get into the cloud, use their glue (lambda, kinesis, sqs etc) and suddenly migrating services somewhere else is a multi-year project.
Do you think that vendor lock in has stopped people in the past (and future)? Thinking about those kinds of things are long term and many companies think short term.
Heck, Amazon themselves got locked-in to Oracle for the first 25 years of Amazon's existence. Vendor lock-in for your IT stack doesn't prevent you from becoming a successful business.
True, true (and heh, it was me who pushed for Oracle, oops)
But ... the difference is that Oracle wasn't a platform in the sense that (e.g.) AWS is. Oracle as a corporation could vanish, but as long as you can keep running a compatible OS on compatible hardware, you can keep using Oracle.
If AWS pulls the plug on you, either as an overall customer or ends a particular API/service, what do you do then?
Do you think that vendor lock in has stopped people in the past (and future)? Thinking about those kinds of things are long term and many companies think short term.