It's simple, you are not stuck with a vendor.

A practical example that happened to my employer recently : we migrated to Microsoft Azure when they opened two datacenters in our country. We didn't have to change any code because we don't use vendor locked solutions.

Any time you want to leave that vendor. If they up their prices greatly, reduce service levels, refuse to give attention to improving service levels.. break a clause in the contract... an so on.

While this is true in theory, I don't recall a single instance of AWS increasing pricing or reducing service levels - not saying that is impossible, but it hasn't happened so far (at least that I remember)

When you deal with google cloud and they up their price. Didn't see it with the other vendors though.