Many cloud providers offer A service unavailable elsewhere. Examples include AWS lambda and Google Bigquery. If you built software using one of these services, you couldn't just pick up your code and deploy it elsewhere without major code modifications.

For comparison, let's say you're on AWS and only use cloud agnostic dependencies--Postgres, Redis, Memcached, and so on. You might have to change config variables, but you could otherwise move your application over to GCP quickly.