Because if it weren't for works that are on the fringe, everything else would remain stagnant. These types of things are beneficial to the industry in that they are risky both in narrative and aesthetics, and prove to be testing grounds into what larger scale anime companies can adapt successfully into the mainstream. The good parts are adapted into the fold, the rest is left for the hardcore fans to absorb and fawn over.
DAICON was considered "weird" and most definitely out of left field, but it proved to be the genesis for one of the biggest turnarounds in the anime industry. That's the point of these types of things: to present to the audience something new, and hopefully have it make some sort of impact.