Because my main business is delivering coal. This forum is just a side project at the moment and as the poster stated above I'm not interested in providing free advertising for them. I've worked long and hard to get both of my sites placed well in the search engines and continue to do so. The is also a lot of work that goes into maintaining this site, for example you'll notice there is 0 spam here. That's not by accident, plain vanilla phpbb install gets hammered by spam. I see no reason why I should allow my competition to benefit from the work I've done. It's not my fault they missed the boat.
FYI bandwidth and storage are a non-issue, both are cheap and I'm only using about 5% of each that my current plan allows. Feel free top upload as many pics as you want. Because the pages are dynamic the SQL conqueries followed by the CPU usage could be an issue in the future. At my estimate my current plan can support about 200-300 heavy users viewing multiple pages. posting etc. That would be in addition to another 700-1000 average users viewing 1 or 2 pages. If it gets to the point where I'll need it I'll upgrade. I'll probably have my own server by then as I run a few other sites unrelated to the coal business as well.
Getting a site hosted is fairly cheap nowadays. It's the building and maintaining that will cost you the mullah.... That is unless you know how to do it yourself.