Sure, there are many contributors to the reduction in scanner sales...
1) Online streaming (I have no clue by how much)
2) Encryption (this can be a big one since newbies generally wanna hear the cops).
3) Radios that intimidate newbies once they read about them.
4) Radios that look like they'll take a month of Sunday's to understand how to use. (No great if you don't have a lot of time).
5) The hobby not coming to the attention of others, like back in the day when radio magazines were at the grocery store.
There is one thing that we do have some control over though, and that is making newbies feel welcome. If they are going to go through the effort of signing up and posting a question, it's probably fair to assume they are interested to some degree. However is some self-appointed expert or ego maniac blows them off or belittles them, many will lose interest on the spot and never buy a radio, let alone call back and become a productive contributing member. I've even seen a place where a moderator drives people off. Talk about cutting off one's own nose to spite their face.
I and others were lucky here, we had great people to answer our questions. I would have never spent what I did on my SDS100 without other people's opinions, advice and insight. I'm willing to bet this site is responsible for a lot of sales, all the way from lowly CCR's to high end SDS's.