1. Jacob massively underrates his products. People take this as being magical. He prices them comparatively to each products actual performance though, so I don't see why this is such a big deal.
2. Sundown has been the current forum boner for a year or so now. Before that, DD had it's turn for nearly a year, then DC had a very short lived one. Some people will flock to the next brand (Skar would have been it if it were owned by someone different), but those that actually used the products extensively and had good luck will continue to support Sundown for a while to come.
3. It has enough presence now, clueless people might be tempted to actually take the advice and buy it. There are quite a few good "budget" brands out there, cheaper than Sundown but they aren't known well enough for someone new or clueless in the business to take them into consideration. Sundown has earned its name by superior performing gear and excellent word of mouth. It is a solid buy for people that want to be louder than their local competition, but not have broke the bank getting there.
4. It is a product that is great for abuse of "clueless" consumers. With those severely underwhelming ratings, most Sundown products can take the over-rated abuse a new to the game consumer is going to place on the products. This makes them happy, and want to stay in the car audio game. This also gives them a drive to upgrade down the road.
That's my ideas as to why it's pushed so much, and even with 0 personal experience myself; I'd say it is a pretty solid option to budget builds or newcomers for those reasons. Yeah, we probably hear it too much, and in situations we shouldn't, but most of the time it is a valid contender for the customers' money.