I think a lot of it is that there just aren't as many developers that know it compared to the other tech stacks. Part of the reason for that is that if you're

I think a lot of it is that there just aren't as many developers that know it compared to the other tech stacks. Part of the reason for that is that if you're starting out as a web developer trying to build stuff for fun, you're probably not picking .NET as your tech stack when there are options that are freer (both as in beer and in speech), easier/cheaper to deploy, and have a more active online community that can help you if you get stuck. And ultimately, if you're a company that is picking a tech stack, you ultimately need to hire people to work with that stack, and it's a lot easier to find people that know Node/PHP/React/whatever than it is to find people that know .NET.