I've never implemented it, but from a user standpoint, there aren't any widely-available services that people seem to use. gchat appears to be shutting their endpoints down. Facebook shut theirs down in 2014.

People got familiar with email because their ISP/employer provided them with an email address. Eventually it became a thing on it's own. Chat was never like that. There was always one service you used, and all your friends used. Now that's gchat and facebook chat.