I appreciate you posting a more comprehensive reply about your feelings on the subject!
Personally, while I do use my smartphone like you (lounge on the couch and read, check social media, etc.), by and large I am sitting at my desktop because it's where I work as an artist. I prefer using the internet on my desktop overall because it's not as clunky feeling to me. I feel like mobile versions of websites are often really squished and cluttered and kind of a pain to navigate.
And when it comes to Tapas, the mobile app just doesn't have all the same functionality. They closed the gap a little recently, but the app still doesn't have notifications, wall posts, or the forums... so by default I just prefer using the desktop version if I'm interacting with the community or finding new things to read. I mostly just use the app when I'm out and a comic I'm subbed to updates.
But, I also am old enough to be one of those people who remembers webcomics before there were platforms like Tapas or Webtoons. So that could be part of my preferences as a reader. To be fair though, I also didn't read many webcomics back then because of how tedious it was having to click "Next" for every page and had to remember to check the sites for new updates. Finding Tapas changed that for me and made it easier to read, even on desktop. I read more webcomics now than I ever have.