Having heard the arguments before doesn’t make them go away, or make them incorrect.
I think you underestimate the effect of globalisation on everyday life, and the attached need to deal with people in far flung places. I work for a small manufacturing company that is based in rural Switzerland; one of about five or six in the world that make this sort of product . We have a couple of customers in Switzerland, but 50% of our business is in (read our output is sold to) Asia/Africa/LatAm. We may ship contracts back and forth for signature, but the negotiation takes place face to face, not to mention signing-off production, dealing with QC issues, etc. While my industry may be small, this pattern of travel is common in many other sectors.
What may have reduced quite drastically is company internal travel in FS, consultancy, etc. The London office no longer travels as much as it did to the Hong Kong office, or the Singapore office to the Lagos one.
As a result of the above, I’d say that it’s the reverse, about 80% of the business travel that does occur is necessary.