Nice post. I also homebrew. What types of styles are you talking about that you can find in a store? I'd love to try making them :)
The one that drew me in the first place was mild. As an example, they recently covered it on BrewinWith Style and were unable to find any commercial examples locally. Things like altbier can be difficult to find, at the time some of the Belgian styles were very underrepresented. These days for me it's a lot of the more regional British variations but that's also because that's what I've grown to like in general.
Take a spin through the style guide and ask yourself on each one "how often do I see these" when they list the commercial examples. And then nite that oftentimes those examples are stretching things a bit already
I agree w/ your general premise about it being for the hobby (that's 90% of why I homebrew) but disagree with the above statement. I've known homebrewers who absolutely brew because it's cheap - I'm sure you've encountered them as well. These are the people who calculate the price per ounce and then proudly talk about how their Great Homebrew is cheaper than Crappy Macrolager. I know many people who do it because it's better than store bought, although that's becoming harder to justify as craft beer becomes better & more ubiquitous it's exceeding the capabilities of many homebrewers.
Another factor you left out, and what originally led me to homebrewing, is homebrewing because not all styles are easy to come by at the store. I started brewing because it was the only way I could taste certain things without traveling to their homelands.