It'll further dilute the "exotic" branding. There are exotic weapons I want, but don't want to buy them. Finding something that is rare can be a lot fun.
Yeah, I think I would have rather Bungie not had an exotic vendor at all and just have them be part of the loot tables for the last bosses of the level 28 versions of the strikes or Nightfall or something.
I'll buy them, since Xur does exist, but I think they lose some of what makes them special when you can just go and buy them.
Also makes for a far less interesting story if someone were to ask, "How'd you get that badass gun?" or whatever.