Currently livechat is only available via the web url. If you have the rocket.chat client open and logged in as a registered user there is no place to start a livechat.
In a larger org its very possible you might use livehcat for teams/groups but it might also be used by the corp helpdesk. In which case, asking regular rocket.chat users to hit a webpage when they are already in the chat app is not the best.
While the helpdesk can have its own room, its not the same as licechat where you want the “distribution” feature to an available tech.