Folks have brought this up before. The main issue is, as folks have pointed out, the low chance of success. Even the older extremes have mechanics which, if not handled carefully, will wipe the party - and Duty Finder opens you to, frankly, any schmoe that wants in, regardless of whether they're capable of handling, or are even aware of the mechanics. Those schmoes often CAN learn the fights, but it may take several attempts. Without incentive to help during those initial, doomed attempts, folks will be leery about wasting their time.

Under the current system, in which a player is rewarded only for the win, it is unlikely that folks would ever touch Extreme Roulette. For Extreme Roulette to work, players would need to be awarded based on willingness to stick it out. Give folks an award equal (or maybe even surpassing?) that of a victory, if they stay in the run until the 60 minute timer expires. (There would also need to be checks in place to make sure they actually participate; not just signing into the fight and then going afk for 60 minutes while they eat dinner, or whatever.)

The reward would need to be pretty substantial, as well; folks could be doing a lot of other things with those 60 minutes, and the Roulette would need to account for that.