Agreed.. There is some satisfaction to building your own, but for people with little or no carpentry skills, kits can be a godsend. After putting it together, there's still wiring, artwork, controls, monitor, computer, etc to be built, so it can be just as satisfying for someone to build from a kit.
After the amount of wood I went though, tools I had to buy, paint, etc, it cost me WAY more than $450 in wood and tools to build my cabinet. I have 0 carpentry skills (which makes me that much more impressed w/ myself for building my cabinet), but for someone on a tight budget with no carpentry skills, it's worth it.
Note: people don't get blasted for spending $300 on an empty cabinet and mame-ing it, so why should they get blasted for buying a kit and constructing it themselves?