I agree fully. If you are going to go to the trouble of a marine tank, there are tons of cool saltwater fish that you can keep. NO need to keep freshwater fish in a marine tank.
Plus, it's a TON more difficult and expensive to keep up a marine aquarium, so why would you want to if you are going to keep freshwater fish in it that can just be kept in an easy to maintain freshwater tank???
I could be wrong here but I think once certain marine tanks mature and become fully established, they can be easier to maintain (in some ways) than certain freshwater tanks. Also freshwater tanks can be just as expensive as a reef tank. I'm not talking about your average 29 gal
blue gravel-bubble wand-tetra hob filter-incandescent lighting freshwater tank lol, but super high tech planted, highly specialized ca/sa biotopes and riparium/paludarium tanks can be really, really expensive and time-consuming. My current freshwater tank is average to say the least (and nothing compared to the monster tanks out there) and it has about 1200 bucks in equipment only (lights, filtration, pumps, heaters, media, water testing equipment) without counting the price of the tank itself, the fish, driftwood, rocks and substrate, maintenance costs, etc.
I know what you mean though, it just kinda bothers me when people look down on freshwater just because they believe "it's cheap" or "it's easy" by default. It really doesn't have to be, there's as much variety in freshwater as there is in saltwater. I've been asked "what do you keep, salt or freshwater?" and when I answer "freshwater" people just immediately assume I have a fish bowl with a goldfish in it and look at me like "eerrrrrrr.... that's cool lol, must be interesting!"
[/end of rant]