SCoB (or Coil in general) isn't exactly the same degree of tedious nitpicky difficulty that Alex Savage is though. Proof being the amount of effort it took to get even the very first clear for each floor, compared to what it was like before. It's true that the fact that it's familiar surroundings can have an impact on how quickly it can wear on someone, but it's hardly a large reason for it. If it were a universal fact, and not simply something maybe a very small selection of people weigh heavily on, we wouldn't have people doing what they did to get their clears. We automatically associate Savage as it's going to be the hardest thing to do atm, especially given how long it took the best groups out there to do it, thus we naturally lower our own morale by a default even if by a small amount (resulting in a quicker response to stopping).
Something to keep in mind is that Savage is literally designed for the best of the best. I'm actually willing to bet that the rate and number of groups at which people are clearing Savage is actually intended and going according to plan. Maybe they'd have hoped for a bit more (or less) people to have cleared stuff by now, but not by anything truly noteworthy. If you're not among the top tier of raiders, you're going to be incapable of clearing it until you get better gear (even if it just means a couple pieces). Any effort before that is simply burning yourselves out, assuming you're going that extra mile to achieve what is essentially impossible for a specific group/person. Not just attempting for the experience. Not everyone is going to perform in the same dedication, effort, and consistency as these top tier raid groups, so other players need to accommodate for that fact... even if it means simply being incapable of it for a short while. Again though, not everyone is capable of handling themselves in the same way. It's very possible that all the wipes that people went through before, learning Coil and whatever else, has taken its toll and shortened some peoples willpower to continue as many attempts now. That's exactly how burnout works, and is rarely ever exclusively attributed to one specific thing. It's a build up of frustrations and relief, given time to saturate in our minds as nothing more than a memory to reflect on (negatives and positives), and apply that to what to expect now and how far we're willing to take it given the past experience.
Perhaps it could just very well be that for some folks, the repeated use of the same environment and boss types is enough reason for you to not bother with Savage, as you've indicated. Everyone has their own ways of finding boredom in something, this could be yours.