I think the usual argument is that Ti lasts longer but carbon lasts for ages if you don't crash it and the people willing to spend $10k on a bike usually welcome the chance to buy a new one every 5-10 years anyway.
I have 2 carbon mountain bikes that I've put thousands of miles on. Both are about 7 years old at this point. Early carbon as a bit fragile, but newer carbon seems pretty damned solid.
Even if you do break them, they are repairable. My wife broke the frame on her bike not long ago and she wound up getting it repaired. It was surprisingly affordable and the fix is likely stronger than the original.
There is also the old saying "If you don't tell the rest of the group ride that your bike is titanium, it will transform in to aluminum."
Another argument against titanium is that mining and purifying of titanium is not so easy on the environment. If that is important to someone, it might get counted as a factor.
My understanding is that with advances across the industry, it's pretty easy to build a bike under the UCI minimum weight, which suggests that you could make the frame out of whatever is best for the application.
You can get stupid light in Steel, Ti, Carbon, Aluminum, but once you're in the sub 16ish lb range, you're going to be going with superlight parts all around, as there's just not that much frame left to make light.
You can make a fully equipped (steel) randonneur at 20lbs, with fenders, rack, pump, generator, and lights. It's not cheap (~10k+ is my guess), but man is it a well crafted bike. With some care, I think that style bike can be done with common components and off-the-shelf frames in the 25lb range.
Rodriguez is advertising production steel bikes at the 14lb level: https://www.rodbikes.com/catalog/outlaw/outlaw-main.html Yeah, they're pricey. (10k) (That's production vs custom frame, meaning that they might have one off the rack in the right measurements, if not it's a couple of hundred to do a custom geo)
But superlight Carbon is going to be up there too, and it's going to use basically the same parts, +- bottom brackets and such. And frankly, I would trust superlight steel before I'd trust superlight carbon.
There are some pretty awesome Ti bikes as well, including custom 3d printed lugs, cranks, forks, stem, etc. They are in the same weight range, and IIRC 8kUKP.
If you're looking at commercial production, probably fair that carbon is going to be lighter. But the the people pushing the edges aren't limited to that.