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.