I think that there are a few reasons.
I'm happy to go into the chat room, but as most people will find, no one knows when others will be there.
Some people simply don't like chatrooms as they're shy or don't speak English too well.
As we have members from many different countries, you have to consider the differences in time zones too.
Some people just don't realise that the chat room is there.
If you'd like to get people into the chat room, how about inviting people in a post, telling them the day and time that you'll be there? Try making it sometime when the most people will be available - remember, many of our members are in the USA which is between 5 and 8 hours behind the UK.
If you name a date and time, I'm happy to join you, depending on work, though I do often work nights
Cass x