Unfortunately, too many people have no sense of what is a fair trade. Calafox is right, hope never dies. Maybe someone will trade them that high level legendary.
I have heard reports that us Europeans are generally a fairer bunch. In particular Germans. So when you're looking for a Pokemon, try choosing Germany as the country to see if that works. If not, then other European countries like UK, France, Spain and so on.
BTW there is one other reason you might see Reshiram lv 9 and under - to exploit the trading glitch. If you put a Pokemon like Boldore in the GTS, then search for another Pokemon and do a trade, when you take Boldore out again it will evolve. People ask for low level legendaries so their Boldore doesn't get traded away. (This worked in previous games, haven't tested with BW though.)