Does this happen? I think I've only experienced something close to this in high school, but never as an adult. Normally, people around me are either supportive or indifferent about someone learning new skills.
Yes, it does, especially when it's something people think is weird. I am a guy in my 20's and recently started learning to knit and I still have people telling me not to do it because it's weird. You just have to do what you want to do and give 0 fucks about what others think
Knit your heart out man! I'm a guy in his 40s who always wanted to get a physics degree. So I've bought a bunch of textbooks. Still at the beginning and learning calculus.
Sure, people are gonna be supportive, but there's definitely a peer pressure along the lines of "but how is it gonna make you rich or famous" in way too many fields.
I think a lot of people use this as a way to start a conversation about what the person is doing and don't think to ask it in a less confrontational way. Some people can't handle seeing someone doing something that they thought they can't or shouldn't do. Most people don't care or see another person doing what they please and respect that.