If you built everything in proprietary infrastructure, porting is a lot more work. Using lambdas tie you to AWS because as soon as you use a few step functions

If you built everything in proprietary infrastructure, porting is a lot more work. Using lambdas tie you to AWS because as soon as you use a few step functions, or you have a few lambdas interacting, changing to Azure or GCP becomes a huge pile of dev work and QA. Having everything "just run" on linux instances let you be perfectly portable and now you can actually shop around.