Technology lock-in without vendor lock-in isn't that huge of a liability. A popular PL under an appropriate license isn't going to disappear tomorrow, and its creator doesn't have the power to hold your business at gunpoint. Conversely, B/FaaS providers upon which you truly depend definitely can extract (or by disappearing simply destroy) much more value than you originally anticipate.
[1] If you use Wolfram Language or Matlab then your choice of PL causes vendor lock-in, but most PLs aren't like this.
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.