This is easily the worst part of M+, as well as raiding when the trinkets are boring, shitty, uninspiring, or raid-leader rage-inducing (LOOKING AT YOU, SLIVER >:C).
However, it's an incredibly amazing design that keeps dungeons relevant and fun, and I can have a nice, challenging, experience in ~17-20 keys that I don't need to schedule time for (though still do w/ my group), and in the same content, I can have an incredibly relaxing 10 key for my friends'/guilds' alts, or sell keys and get some gold for it. Not to mention, both pieces of content can get me gear upgrades, and at worst, if I'm doing at least a 15, I'm guaranteed a Veiled Crystal, and if I'm helping F&F&G(uilides), I'm also getting brownie points w/ them with the chance of a veiled crystal (or a potential lucky TF or neat mog).