It's basically a comparison of two functions. On the one hand is the overhead of needing to schedule and maybe travel in order to meet, and amount of time waste

It's basically a comparison of two functions. On the one hand is the overhead of needing to schedule and maybe travel in order to meet, and amount of time wasted by people in the meeting who don't actively need to participate. On the other is the cost of context switching, risk of misunderstanding inherent in lower-bandwidth communication and delay in understanding one another that comes from asynchronicity. Whichever is more costly in a given situation loses out. In my experience, if the conversation would require a lot of back and forth (e.g. complex or delicate topic) synchronous wins, otherwise asynchronous wins out. As async tools become better, the cost of async goes down, and it comes out ahead more often. It's not always the best solution, but it often is.