Well, you can see that mirrorless is being slow to be adopted and people are still using DSLRs - despite the fact that mirrorless are much smaller and lighter. From what I understand the Canon 5D series was still the best selling camera in 2019, according to an article I can no longer find. Canon and Nikon were very slow to adopt mirrorless and the technology wasn't as good as other brands, I'm not sure but they have probably improved them since then, though.
Mirrorless has been gaining steady grown but slowly, and press photographers still use DSLRs for the most part, it seems, if you look at photos and videos of press conferences, you will rarely see a Sony A7 series camera. Most if not all are Canons and Nikons.
When I went to best buy last year they were pushing Canon DSLRs to me - touting them as being more durable and tankier than the more fragile mirrorless cameras, and DSLR lenses being more plentiful and cheaper on the used market.
I think people are often "wowed" by the sight of a large camera, and size of gear still gives the appearance of professionalism - walking around with a small micro 4/3 camera doing press photography might be seen as amateurish even though it's probably perfectly fine.