Entry-level buyers are rarely much concerned about buying into a system. A fair percentage of them never buy any more lenses than the one or two they get with the camera.
Even I, who had once been rather serious about photography, bought my first Rebel as an impulse purchase. I stopped into H. H. Gregg to look at TVs and washers and dryers. I saw a good price on the camera. The deal included a case and some odds and ends, and for an extra $100 I could get a 75–300mm lens, too. With the kit lens that gave me the equivalent of 24mm to 480mm range, so why would I buy anything else or worry about an upgrade path? I took many good photos with that equipment. (When I was a kid I took many good photos with a Kodak Brownie, though likely not as good as the pictures that Ansel Adams took with a box camera.)
As it turned out, I did over the years spend thousands of dollars more on Canon cameras and lenses, but that was not my concern when I bought the first Rebel. I can easily understand folks who buy entry level cameras without thinking, “How will this affect me ten or fifteen years from now?” I was one of them. As it turned out, in retirement I wound up more comfortable financially than I had anticipated, and I wound up devoting more of my time to photography, but I didn’t know that in 2007.
(And I realize things have changed somewhat over the last 15 years, as cell phone cameras have gotten better, and a lot of folks are mainly just taking pictures of themselves. So the number and range of folks buying entry-level cameras has changed. Stats suggest that the cash cows for camera makers tend more toward Rebel and M class than toward TS-E lenses or the R3.)