Whether you've got 3 coins or 300 from weekly/nightfall makes no difference to the fact that they are still earned. And whether it's "easy" for you doesn't make it too easy for others who don't have as much time or skill to get coins. Xur isn't for the hardcore or 1000 hr player, he's for new players and those who struggle to get exotics from anything. And it's not really your business if someone splurges on 6 gjallarhorn just because you don't.