I understand this point of view but let's pretend for a minute. If the competition didn't have it, would you demand Canon to have it ? In the past year I have seen 90% of the desire for Canon products to be keeping up with the Sony/Joneses...not asking for bodies and lenses for the sake of particular shooters needs.(meaning, they always mention Sony) I couldn't give a rats tuchus what systems which I am not invested in have features others are using. But that's just me I guess, everyone else is in the 'Play catch up Canon/Canon is *******' race. Perhaps it's the Ebay culture of easily parting with and selling your goods (which I find to be a major PITA) for others that fuels the GAS and self deluded needs.
Could it be the understanding that digital imagery is in it's infancy and I'm still clinging to my film based curmudgeonly views where folks did just fine with much much less?
I don't need no stinking IBIS, the glass stabilization is more than fine, especially the new 4+ stops lenses.
I understand where you're coming from, and the short answer would be, if your current gear is working well for you, then no.
But, there's also the side that if a brand wants people to buy something new/extra, then they have to add something in there too; people who feel their gear isn't doing what they want, and are looking for an upgrade, will also often be looking at what might fit their needs. For some, being able to stablise primes with IS might be the feature that gets them buying something new.
I know when I was looking at upgrading from my old 6d, I was definitely looking at what other brands were offering, to see if they had what my situation needed. But, it also wasn't until I saw what other people were able to shoot/capture that I started to think the 6d wasn't actually fitting my needs - until then I'd more or less just assumed what I wanted to get were shots that weren't really possible
I think what canon should be considering is not everyone may be happy with what canon are offering in their current models, and needs to be enticing people with features that make them seem like a good option/value. Ibis is one of those things that is useful enough that people will only look at options with it - one family member herr hasn't bought a fuji XT-3, only duet to it's lack of ibis
Edit: above is just about ibis and canon adding/not adding features that sony/nikon etc may have - I'm not meaning that this camera won't appeal to anyone if it doesn't have ibis, just that some people may pass on it for what it lacks, rather than what it adds. I'm sure there'll be people where one particular feature isn't a priority