It's not meant to be worthwhile to dump into it. It's there to prevent the tickets from feeling wasted if you otherwise couldn't use them in any other way.
Since the next cheapest item you could redeem for is a key fragment for 40 tickets, at most 30 tickets will end up getting dumped into blue essence.
Lots of games do it. A special currency that can only be obtained a certain way that, for example, in an RPG setting, only has a potion or something as the cheapest thing you can buy, with the other rewards being significantly more worthwhile such as equipment, cosmetics, or items that can enhance your skills. The potion being a horrible buy is self-evident, but it's there in case anyone doesn't plan on getting any more of that currency (or can't) and wants to get rid of it. (usually to clear up inventory space) In this manner, they aren't forced to just trash the currency, and can still get something out of it, even if it's not as good as the other rewards.