This is because they have entrenched themselves in a comfortable position that they don’t want to give up. Most won’t admit this to be the actual reason.

Think about it: you are a normal hands on self thought software developer. You grew up tinkering with Linux and a bit of hardware. You realise there’s good money to be made in a software career. You do it for 20-30 years; mostly the same stuff over and over again. Some Linux, c#, networking. Your life and hobby revolves around these technologies. And most importantly you have a comfortable and stable income that entrenches your class and status. Anything that can disrupt this state is obviously not desireable. Never mind that disrupting others careers is why you have a career in the first place.

C#?