I mean, I like Firefox, but I’d love to see Vivaldi based on Firefox/Gecko. There’s Floorp, which is similar in some ways but it’s more like an Edge built on Firefox than Vivaldi.
Edit: Thank y’all for your answers. :D
I want to link !@bdonvr@thelemmy.club 's post because it is a similar quesion. https://thelemmy.club/post/718914
I’d imagine because they want as little compatibility issues with their product as possible so they just copy what’s already popular.