For most of them, it's a huge money maker, actually. I don't know of any that will give you a refund without a water sample, and even though while the fish are alive they'll tell you 3 ppm ammonia is just fine, when you're there for a refund, the slightest trace of green and you don't get it, but you are given an explanation of why they recommend cheap hardy fish at first, because by the old school cycling methods they give (fish in, minimal water changes, mabye some salt to help with nitrite poisoning) the first fish in are highly likely to die. Some of the "good" ones will give you a discount on some more hardy fish to continue the cycle. They're not entirely clueless. They know the cycle process can kill - that's been standard hobby knowledge for a century, and they make return policies that won't cover any water quality problem they can test for.
I'd also like to add, cycling with fish is not faster than cycling without, as the OP seems to have been misinformed. A fishless cycle can finish in 3-4 weeks. With fish regularly take 4-6, and are vastly more work.
At the end of one, too, stocking increase is slower, as well. Normally, as said, you use about 1 inch of fish per 5 gallons to cycle. Afterwards, you can't add more than about 10-20% of your current stock at a time without a mini cycle. I've done a fishless cycle, topped up ammonia for an extra week (whole process took 4.5 weeks, cycle finished in 3.5) and overstocked the tank right out of the gate with nary a hiccup (about 1.2 inches per gallon). I don't recommend stocking quite that quickly, but it's more likely to work than Nick's flawless cycle with fish. Browse on this forum, there are hundreds of threads, some of which were ongoing for months, of fish-in cycle disasters, and I'd say one in five had that sort of happy ending.