there is a trade off here. You can ether have some vendor lockin or you can have secure and scalable solutions that are updated and maintained with little to no effort on your part.
For example. I have 2 Google accounts, one that I use for everything that is important and another that is use to junk ect... My main account is 2 factor Authentication on it and has a very secure password, the other one only has a secure password.
These are 2 very different use cases and for you to have to code all of that into you own app and maintain all the data on top of that is a lot of overhead. APIs like this get rid of all of that overhead and I for one am very happy to be able to use them.