> In a call you can't be ignored or left on read for 4 hours.

You also have no time to formulate a thoughtful answer to complex questions, though, which is one my issues. Calls are fine for some things, but 90% of calls could be an email because they contain discussion that needs more than 15 minutes of thinking. And a lot of the time, these calls need a summary email to even keep track of what was said!

I think the gap issue in async communication is a feature, not a bug.