Basically it's not that traditional media is inherently bad, it's just that it's often easier, faster and more cost-effective to get a polished result with digital media than traditional.
I once had the privilege of visiting the home of the late Ron Smith. An incredible artist best known for his work on Judge Dredd. His comics were painted with watercolours and inked by hand, and they were just.... beautiful. Absolutely amazing. He used the watercolour with a dense mix of pigment to water for rich, flat coverage, and carefully inked them all with a nib pen and india ink. What a legend!
But... He was the same age as my grandparents. He fought in WW2 as a fighter pilot. His generation got paid so much more than comic artists do now.
I also met at a convention, one of the artists on the iconic British SEGA comic, "Sonic the Comic" and saw some of his originals. The colours were all painted with an airbrush! He had a whole dedicated study in his home for airbrush-painting his comics. Er... great.... a room... huh? Where is this room where I can set up a massive drawing board and spray paint around in my little flat that has: a bedroom that just about fits a bed and clothing storage, a bathroom and a kitchen/living room? This guy was as old as my parents so... again, while not so profitable, he still made a decent enough wage off his comics compared to a modern creator.
This lovely, careful approach just wouldn't be fast enough for a millennial creator like me to make a living or make headway on the plot of a webcomic. We're expected to make work that looks just as polished, but in a fraction of the time and cost. Replacing the paint mix and cleaning out an airbrush, having a big dedicated room for our art and a place to store all that Bristol Board? Wow, that'd be nice, but we can't afford that. I think a publisher would laugh in my face if I went up like "excuse me, but can you pay me more money for this work? See, I insist on making it with traditional media on principle and the materials and time cost more than digital..." Unless you're some kind of huge celebrity, whose name alone will sell the books so you're worth paying more for, they will just find another artist who will do it cheaper.
So some people might say "well, just use a cheaper, less space-hogging alternative! Like pencil crayons or copic markers!
The problem is... my work with copic markers looks mostly like a slightly worse version of my digital work. They're great when I need to work out and about or want to produce an "original" somebody can personally own, but I could replicate the look with those nice soft colours and a slight noise effect digitally for far less money. Plus by doing so, I'd never need to worry about accidents like bleeding or a line going wonky ruining valuable hours of work!
And as for pencil crayons.... I'm sorry to anyone who likes them, but pencil crayons are not generally used by pros for a reason. They give patchy coverage that's particularly visible on dark areas, so you get poor value balance and a noisy look. Sometimes you can get proper coverage, but it often leaves the area shiny or even warps the paper if you do. While simple gradients and shading can be done, they can't be mixed, so colours are limited by what colours are in the pack. Then after all that, when I scan it in, I'll have to tweak the balance a bunch and tidy it up to make it look decent and get the white paper actually white instead of a grainy grey colour anyway.... so it feels sensible to just... work in a medium where it's already tidy and has colours that look how I want them when I create it.
Pencil crayons are a cost-effective tool for doing sketches out and about or for people to learn art fundamentals. The only well-known comic I could name made with them was "The Snowman" by Raymond Briggs, which is:
1. Even older than me, done in a time when this was financially viable. 2. A children's book which used the roughness of pencil crayons deliberately to evoke a naive, nostalgic atmosphere. 3. A self-contained book by an already well-established children's writer/artist which almost certainly got an advance from the publisher to fund it and when it was done, it was done and the creator could live off royalties. Basically the exact opposite of a modern webcomic's financial model. and 4. Drawn by a great professional artist. He was already published and successful, his hatching work is lovely and he knew how to make those pencil crayons look great, and the print reproduction is really crisp, done by pros so it looks good.
Basically, if you can make something with trad media that legitimately looks as good as the top performing comics on the platform in a comparable time that it takes for them to make their pages, then awesome, go for it! But I haven't seen a lot of people achieve this feat, and I've certainly not seen any pencil crayons up at the top of the popular categories, and I'd guess that's because it'd take so much more time, skill and effort to make a comic that looks as professional as those digital comics using traditional media.