One reason might be that the tools have telemetry (i.e., automatically gathering and sending data about your system and your use of it to Microsoft) enabled by default[1], which is unexpected and off-putting to people in the free software world. It seems to reflect a very different attitude to some fundamental cultural values.

According to the comments on the issue tracker, it was supposed to be OK because it was anonymized – but oops, there was a bug, so it wasn't totally anonymized. But it's OK because you can disable it if you happen to know about it – but oops, the disabling mechanism had a bug.

Things that are important to many free software users are not important to Microsoft. I was excited about .NET Core until I became aware of this stark misalignment of goals and priorities.

[1] https://github.com/dotnet/cli/issues/3093