I don't get why we shouldn't be allowed to do this. If we only need a trinket from one boss out of 13 bosses in a raid for example, what possible downside is there to me using all of the coins which I have bought / earned for multiple chances at the one thing I need in the raid rather than waiting multiple weeks of only have one chance for it? There's no added advantage to me saying rather than using my coin at a chance of one of these pieces from these bosses, this trinket is the biggest upgrade for me here so I want to blow all my coins on getting it. Makes sense to me.