You're right, of course. I DIY my own juice and that aspect is very hobby-like. I was never on a smoking message board
As a smoking substitute alone, I should say, it's not supposed to be a hobby. In that mentality the work involved in larger batteries (cleaning reusable parts, for example) is detrimental to the experience. At home is one thing, but in my daily, working life, I don't have room to vape in a hobby sort of capacity. I may focus on vaping the most at home, but it's during the work day that I "need" what it provides more.
I also fear that the hobby aspect of it is part of why they are being banned in various countries. All arguments aside we should all be able to admit that electronic cigarettes in general make nicotine delivery very... appealing. Little to no health consequence, cheap enough to go crazy with it, flavors up the wazoo, and accessories for your heart's every desire. It's FUN, so fun that it's a hobby for some. It can be used to deliver all manner of illicit substances. These factors shouldn't eclipse their ability to get people off analog cigarettes, but in the minds of the non-smoking public that doesn't want to "help" make smokers' addiction more convenient in any way, it will.