Web-based tools are stuck on whatever the currently supported standards are and depend on all browsers implementing them the same. It's much easier for a company to simply ship their own code on their own apps and control the entire stack, which is why Zoom was so much better than every other alternative when it came out. I think people forget just how crappy teleconferencing was before Zoom. I used to work for a competitor, and we didn't like using our own product!