I agree there is probably not one answer to the question.
I think part of the inherent root, as folks have pointed out in other ways for years, is that the basis of MU arises from TT RPG and in the small group environment success is generally rewarded more often than failure.
There are quite a few RP'ers out there though that see it the way I do, failure is often a chance for more story and development. This more often arises out of PrP when we ST for each other over events and big things Mu-wide. But we go to get the goods, it comes down to a couple rolls, we succeed and the day is done. We tend to forget about those times, its when we fail and have to recoup, regroup and find another solution that more story is created. This is cultivated rather than assumed by most though. Those of us who do this on Mu also have done this on TT.
I freeform my campaigns as a GM/DM. A lot of other campaigns more and more seem to take a prescribed route, the group has to deiscover the evil demons are taking over the world and eventually stop this, its the overall meta amidst which all the other adventures and sessions evolve with an end point in site. I see a lot of folks prefer this for a Mu* as well. But in my campaigns, the group is prevented with various ideas and mysteries to explore and they choose what they want. I've briefly mentioned it before but long ago during an Al-Qadim campaign I saw a random encounter suggested somewhere of 'PCs find a golden feather' and I included that while they were traversing the desert to cut time between two cities. One character took the feather and wanted to explore it and this developed into the feather belonging to a swanmay sort of being that was a member of the Court of Birds, they decided they liked the swanmay and courting ensued and they traveled to meet the Sultan of Birds the char expressed their intentions they received some crazy quest to prove themselves to the court of birds which involved a challenge that could easily be solved by flying at a time no PCs had access to flying magics (easily at least). I think they spent six months traipsing about this part of the desert in RL time (24 campaign session give or take). Most of it stemmed from series of 'lost' resolutions and figuring out how to overcome and get what they wanted for the character.
Incentivizing a loss to me is rewarded by the extension/creation of story and the development of the char. I think if this could easily be made incentive it would help. More XP to represent off-camera development to overcome the failure, more story time dealing with the loss, then that would help but ...
Folks have in the past pointed out that the incentive for failure would be a lure for folks seeking mechanical advantage, if there is a reward for failing more folks will choose to fail rather than win. I brought up once a different sort of MU based on PACE rpg by Evil Hat (which was free from their site once upon a time). I don't know the name for this genre/type of RPG system but it was based on the karma pool concepts that have floated around in various incarnations. Basically there is good/player pool and evil/GM pool, if a player needs extra successes to succeed they can take from the player pool, add it on their challenge, but this moves it to the GM pool that can be used to help NPCs rolls, bring some bad karma to the group, and other misfortune. I proposed that two players in conflict could also dice/face off, but the player that loses gets a karma point. The issue became that if created so players can do their own stories, some players would milk the system and do duels with each other so one looses to gain karma points.
I guess it comes down to culture, I think it failure is an incentive of its own as a player because I tend to have more memories and create more stories out of it. I think to help it could be incentivized in some fashion but I don't know the right balance to make it enjoyable in some way verses a new way to compete for the shiny by trying to out-loose as well.