I'd imagine a lot of them are cuttable. I have a friend who regularly flies to the US (from the UK) to run conferences. Frankly it's ridiculous that they don't hire someone from the US to so it.
With modern video calling technology, how many business trips are really essential? Some sure, but a lot could be cut, or merged into fewer longer trips.
You're right I think some are overdone. One example is the consultants taking a plane 2x a week (leave early monday, come back thursday eve, often with unconstrained distances). Maybe a bunch of those could be cut, though in that case I think a lot of these business models offer a "premium" service. If you're paying $1M/quarter for a McKinsey contract or for an I-banker or a big 4 accountant you definitely want to see that person physically. Though keep in mind McKinsey is also probably less price sensitive than the average flyer.
Still even with that, I'd like to better understand the economics. If only 12% of trips are business vs pleasure, killing all business trips won't move the needle in the long run. There's some question of how long business trips are, you can be 12% of trips but if they're longer it's worse.
My overall point is that there are a lot of factors in how people chose to travel. It's far from clear that increasing the already quite high price is what's going to deter people unless you tax it massively. In which case we'll effectively return to a situation like the pre-deregulation days where only the rich flew, which may be fine, but should be directly considered.
With modern video calling technology, how many business trips are really essential? Some sure, but a lot could be cut, or merged into fewer longer trips.