That's actually how many covens on here work. The issue is how far one can teach and how willing someone is to participate. I have run Divine Essence for many years and have been council of a few other covens on the site and from what I've seen most people join a coven to brag they're in it. [Like a badge for their profile] yes, we are all busy and many people can only devote a few hours a week to online covens, but sadly most people don't want to put in the effort, instead they want someone to hand them the answer.
I've been in covens who have monthly meetings, weekly check ins, questions in the forums, study groups, and regular meetings in the coven chat. Good in theory but in practice there's time zones, time restrictions, and a user's interest in any given topic to consider. You could try running your own study group through mail and site forums but it requires a lot of time and energy.