The short answer is: People really like em. They might get bored with talk of all the prime lenses in the world, but give em a zoom (of any size) and they'll have a good time. When I worked retail, too, well over half the people wanting SLRs wanted to get photos of their kids playing sports, or something similar, or they'd be happy with point-and-shoots.
(Kit zooms are kind of handy for me, anyway, despite me being all 'serious.' It so happens that I like really-high-quality fast primes of moderate length. While I'd just as soon have nicer of what zooms do, it's just not where my emphasis is on a limited budget, so a consumer wide or a nice cheap tele zoom can come in handy, as long as it's not awful. It's not where I want to spend hundreds or carry pounds, so I have a kit zoom for a real wide on digital till I can spring for a DA 21.
)