From what I understand, it's all about the social perception of the possible economic value that your hobby can contribute to the rest of the world.
The difference between a "geek" and a "nerd" is that a geek learns and practices a discipline with the intention of using it to build economic value. For an example, someone who spends most of his/her spare time learning about computer science and programing is a "geek" if (s)he plans to use this knowledge for his/her occupation or some other activity that creates "perceived" economic value to the rest of the world.
However, a "nerd" spends his/her time learning and practicing a discipline that that is not intended for creating "perceived" economic value. An example would be someone who spends a copious amount of time learning computer science and programing while living his/her life as an established botanist.
People might say, "_____ is such a gaming nerd." While with the former example, people might say, "_____ is such a gaming geek."
As someone grows older, I think that there is a general societal expectation for the adult to specialize in some specific area. Consequently, if your area of specialization isn't computer programing, computer science, CG art, or somehow related to video game design, people may "perceive" this activity to not have any "intended or possible" economic benefit to you or anyone else. As a result, they will generally consider this activity to be worthless.
Even regarding social status, I've seen this concept to be pretty universal. I've known reputable professionals who play a lot of video games with their extra time and are considered "video game nerds" as a result. It's not necessarily a bad thing, but most people seem to perceive that they are "just wasting their time."
In comparison to the social status of these adults, I think there is also the social perception of "which activities" are considered to have the possibility of building economic value. The most popular of these "accepted" activities is probably the discipline of "learning to paint." Many people take up painting and learn all about the different textures, brushes, and artistic forms. Of course, most people consider that these paintings could eventually be sold. In turn, this activity is considered a "hobby" and not a "waste of time." However, from what I understand, most people in general don't see video game design as something that can build economic value. It still hasn't crossed the threshold of being perceived to contribute any value to the world.
It's funny how video game enthusiasts sell their online game character accounts for a lot of money (even now), but most people in the general public still just don't understand exactly "how this works." Consequently, the stigma of the perception that "your hobby is worthless" will continue to stick around as long as the general public doesn't perceive the possible economic benefit of your game making, that it is an acceptable form of meditation, or that it is related to your area of specialization - given that you are a grown adult.
