Companies that aren't mindful of vendor lock in aren't long for the world.

Though those cloud platforms all have their own proprietary components most users are savvy enough to constrain and compartmentalize their use of them lest they find themselves having all their profits taken by a platform that knows it can set its prices arbitrarily. The cloud vs in-house adoption is what it is in large part because the cloud offerings are a commodity and a big part of them being a commodity is that much of the underlying software is free software.