Because when you randomly get an exotic from a drop in raid or strikes its random. If you did nothing to help your team and just sat there the whole time and get an exotic, you didnt earn it. Just the same as even if you did all the work in the nightfall or something and get an exotic and "earned" it you technically didnt earn it because it is a random drop. You couldve gotten something else but RNGesus decided to give you an exotic. You do earn strange coins. It isnt a random drop. It isnt a rewards system based on performance, its based on participation. You do the weekly heroic on lvl 28 and you always earn 9 coins, and therefore earn the exotics you pay xur for. Your logic is to say you found an iphone on the street and took it and therefore earned it, but if you work for the money to pay for one you didnt earn it. Its bullshit.