It depends on what kind of user you're talking about. There are user group that unlikely use forum, for example
1. Bitcoin developer prefer GitHub, IRC or email. Few others prefer twitter or reddit.
2. Public figure who prefer social media to maximize exposure.
But IMO bitcointalk have more rules (compared with other forum) with more strict moderation, which is turn off for users who want to have casual discussion/question.
We are doing good with almost 700+ Users registering everyday.
But majority of them are either inactive or used for all kinds of spam (usually SEO spam and spamming shady website).