Becsue you can get multiple legendaries and legendary does not mean it is extremely rare. You don't get them all the time and you have to save a bunch of marks to even buy them. You can also have many on at a time. They are not the same thing. Exotics are not suppose to be rare the are to make you think about your loadout and play style and what you want yo use and how to use it. That is why you can only have ONE. Legendaries are rare and. You can have as many as you want.