Disenchanting to motes, but not letting players buy with motes decreases the willingness to swap gear with other players who might 'need'/'have more immediate use for it' than you.
1.You can't get an equivalent value in exchange
2.If you ever even remotely might want the piece in the future there's no 'fast' way of getting the currency to do so short of paying $$.
This leads to less people willing to run content with their classes that don't need the gear decreasing the amount of players able to find/fill groups.
I've been running HoRT3B2 with my burglar repeatedly, even willing to do so locked because people would in theory be willing to trade stuff. I already know people who only run if stuff can drop to them which they need. They're the people who won't be running as much after this.
Crell-L85-Champion - Riddermark ; Swego-L85-Burglar ; Kotvi-L95-Runekeeper
Delego-L85 Hunter ; Stodden-L51-Captain ; Edhul-L61-Loremaster
Deglorion - SoA XP Disabler