ssound5rs yes, I know that already. I have photoshop and I use the splice option. it's still annoying to have to resplice and upload all of those panels on webtoon. webnovel doesn't have a need to do more work than they already have, and going through the process of putting their comics on webtoons is effort that they don't need to take.
also, by changing their panels, I don't necessarily only mean just cutting it up. webnovel will also have to reorganize all of their boxes within their panels because of the fact that the popular comic styles are different. webtoons emphasis on having spacing to control the speed/flow of the plot, while many webnovel comics are more of the horizontal then vertical reading styles (e.g. refer to this one quick panel taken from the beautiful wife of the whirlwind marriage here. this will take a lot of effort, especially with the pictures that do not have boxes/background images. at the same time, with the reading styles different, readers may not find webnovel comics as popular.
secondly, there's also the concept of the general morals of readers on both sites. webtoons has a lot more readers who are less ignorant on supporting/glorifying/romanticizing ideas such as rape, date rape drugs, weak females who rely on men, and 90% of webnovel comics directed towards females support those themes, just like their novels.
thirdly, the content that readers engage in differ with the two different platforms. readers on webnovel are already familiar with concepts like cultivation and martial arts, so reading comics about them aren't difficult. for readers on webtoons, most of the terminology they use for cultivation and all of that are completely unfamiliar, and it is unlikely that webnovel will make a guide explaining that for their readers to. therefore, this is likely to draw in less readers. besides cultivation terminology, you can clearly see a difference between the most popular webtoons and the most popular webnovel comics. generally, webtoon audiences like deeper stories with actual messages & aren't just 19204810810289018 chapters of fluff and drama. the content just appeals to different groups, and what the webnovel audience finds engaging isn't necessarily what the webtoon audience does.
I don't see where you're getting this "50,000,000" webtoons reader statistics from. the number is only 10,000,000. source plus, this number is not only for readers in english, since line webtoon covers sites in languages of multiple languages that don't share the same discover platform.
lastly, before webnovel starts posting their comics on webtoon (though I highly doubt a day like that would ever come), they would likely start posting their comics on the chinese version of line webtoon, dongman manhua. their chinese site brings them more money, so they will likely reach out to more of a chinese audience than an english-speaking one.
thanks for coming to my ted talk.