Audio and video chat

I noticed (and have played in games) where people use an outside audio service like discord. It is my understanding the Roll20 supports its own internal audio and video using WebRTC. Why don't more games use the built-in support? What is the disadvantage to using it? What are the advantages to using one of the outside services?

Private reply from anonymous: Roll20's WebRTC is peer-to-peer for every single connected person. Having 5 people connected is around a 5MB upload and it gets worse from there. That's just voice by the way, if you want video too it goes higher. They are working on it, admittedly, but things like Discord are a more tailored system that requires minimal effort on your bandwidth. Also, because WebRTC for Roll20 is still, technically, in developement, it has a sporadic quality of sometimes failing miserably, and sometimes working like a charm. It's a bit hit and miss.