Since the AWB sunset in '04, it's pretty much been all ARs all the time. I think there's a combination of reasons for this- People could once again own them along with all of the features, more exposure with the wars in the middle east (via first hand or media), and honestly the increased use of the internet. Take a look at the countless photo threads on almost any forum and it becomes incredibly obvious that ARs are the cool, sexy solution. It doesn't take long for a lot of people to begin justifying purchases and therefore uses. Before long, some of these people start envisioning tactical band camp scenarios that they "require" such a loadout. We've all seen pictures of the 400lb guys open carrying their ARs. This guy isn't busting down doors, he's playing Call of Duty.
Point being, people start loosing sight of what THEIR mission TRULY is. The saying is the mission drives the gear. The saying should be YOUR mission should drive YOUR gear, because people start basing their gear off of other people's mission, or what they wish their mission was. People are certainly free to do with their money as they please, and there's nothing wrong with good, expensive, cool guy gear. However, it's easy to start down that rabbit hole and begin overlooking many other viable options- i.e. the shotgun.
Once you begin looking at realistic, in the home, across the room scenarios, the game changes completely and this is what the bulk of every day people need to be concerned with when it comes to long gun selection. Most people in the know with a lot of shotgun experience (Tom Givens, Darryl Bolke, Steve Fisher, Chuck Haggard, etc) all agree that shotguns excel at close distances when you need to stop someone RIGHT NOW. Tom Givens' explanation of serving size per bad guy in regards to ammo capacity is fantastic. Basically, a typical response with an AR is 5-7 rounds, so you probably only have 4-6 servings in an AR mag. The typical requirement for a shotgun is 1-2 rounds, so most defensive shotguns will have 4-6 servings (often more, because there are not many cases of shogun uses requiring more than 1 round with a good hit.) Not only does this negate the need for "high capacity", but factoring in the split times, you're going to spend more time shooting a the AR than you will the shotgun (based on those stats).
With Flight Control, there is a far less likely chance of stray pellets. You can put the round where you want it. I've seen some people say that shotguns take more training. Not really, it just takes very specific, good training. Pump guns are great for the budget. Stepping up to something like the 1301, it's an incredible home defense option. It's lighter than an 870, split times are lighting fast, recoil is very mild, and it's insanely reliable. Especially in a place with restrictions that seems like an incredible option. I have no restrictions where I live, I have a couple ARs and an AK, and the 12g (1301 specifically) is currently the long gun of choice inside the home.