This site/web space is paid for by the creator, he/they then try to make some of that coin back through sponsers(don't know if neo actually charges sponsers or not).
Shirts could bring revenue to the site but someone has the front the cash, find a reputable company to make them, etc. Plus some want catfish, some want bass, some want arrows, etc. Then factor in half the people who say they want one, won't by the time they're made. So it's more complicated then getting 300 catfish shirts made and knowing they're all sold.