Because they’re “inexpensive”, which was the main qualifier in the question. (Although I don’t own one.)
Note first my recommendation was “used”.
If a person is going to purchase a gun strictly for home defense it probably isn’t going to get shot a lot. You don’t need a high dollar weapon to just collect dust in the corner.
Really good point. I bought my defender used because we don’t shoot the shotgun much. Just enough to be confident in it. We do shoot the 22/45 and 10/22 a lot so those we bought new. But you can get good deals on 12/20 gauge used shotguns lots of places.