An impression I have is that it's still easiest to spin up a simple cheap Linux box on many of the server, VM, and "cloud" providers out there. Open Stack for the most part has avoided the question of Windows Servers. Even (especially?) Amazon's EC2 has supported Windows Servers for a while, but it still has heterogeneous pricing from Linux and fewer options...
I don't think Microsoft is trying to stop people from using Windows as a back-end server (especially when you look at efforts like Windows servers as Docker container farms), more that they are trying to even further lower the barriers to entry that a small "garage" company can spin up something like SQL Server. Maybe as that company grows past the "cheapest VPS on the market" phase they look to running their own Windows servers or (I presume, better yet to Microsoft) let Azure manage SQL Servers for them...
That said, they'd still have to come up with a much cheaper license for SQL Server to entice that "cheapest VPS on the market" crowd, but certainly this appears a step in that direction.
Saw it pointed out in other comment threads too that SQL Server on Linux makes it possible to Docker-ize a full application stack with .NET Core today, while you wait for the eventual promised Docker support for Windows containers... This also seems a possible motivating factor.
I don't think Microsoft is trying to stop people from using Windows as a back-end server (especially when you look at efforts like Windows servers as Docker container farms), more that they are trying to even further lower the barriers to entry that a small "garage" company can spin up something like SQL Server. Maybe as that company grows past the "cheapest VPS on the market" phase they look to running their own Windows servers or (I presume, better yet to Microsoft) let Azure manage SQL Servers for them...
That said, they'd still have to come up with a much cheaper license for SQL Server to entice that "cheapest VPS on the market" crowd, but certainly this appears a step in that direction.