Is that your own observation or do you get the data from some other source? (Google Analytics) ?  There are different time zones, so if that is your own observation, then you might miss the "active" chat users that are online in other time zones.

I can say from my own experience, chat numbers have been stable and slightly growing over the years. I started gambling at Stake when the "rain" requirement were much less than what it is now.... and even with all the rain farmers, Stake chat had about 3000+ users per session.

I think with all the counter measures for bots that has been implemented by Stake, numbers have been kept under control... so we are just seeing genuine players now.