I don’t understand why voice chat isn’t more popular at work. It’s the top choice for talking with friends and family (phone calls and VoIP).
I'm in consulting and the guys who are willing to be on camera have way more success with their clients than the guys who aren't. I learned to 'do conference calls' when I was younger and playing WoW with my guildies so I scoffed at it, but seeing really is believing. You are more likely to land a sale, get fewer objections to your project roadmap, your clients are more engaged with what you say... just everything is slightly better.
Video gets more info about how certain, cooperative, serious, how well listening etc people on the other side are. Also the relationship (boss/right hand etc) between speaker and non speaker on the other side gets more obvious.