> Once you've written a bunch of code in a language, you're pretty much locked in - without a massive effort - in any event.

The difference is one doesn't have access to Lambda infrastructure itself. IF I write an entire app in XYZ lang, I can still run it on my own server or make it an executable and call the code through RPC. If I base all my work on a third party vendor infrastructure I can't replicate it requires an even more massive effort to migrate to something else, because now I basically have to re-write my app from scratch. FAAS may have killed BAAS but isn't going to kill PAAS.