I've never had problems enjoying or liking flight or space simulators, ever, and I've only once seen a single game that required you to have a joystick to play effectively. The only joystick I had as a kid was an "idfltstick," or some strange spelling like so, and it didn't last long. So I continued to use the keyboard and the mouse for a very, very long time. My Extreme 3D Pro is the second stick I've ever had, for that matter (and it's much nicer than the other stick by a long shot).
That said, I think that flight and space sims get a bad wrap in the minds of a casual gamer as they require a much more labor-intensive style of play to master or be proficient at. Flying a space ship or an aeroplane is not easy, and a sim tries to be as realistic as possible. As a result, sims tend to be - get this: hard. For that matter, I love this example... one of my friends was impressed by me murdering Shivans with dumbfire rockets in FS1 with the Athena, so I gave him a copy of FS1 to try out. He just couldn't get it, or into it.
That said, hardware IS an issue, but not like you think: his laptop did not have a numeric pad, and re-configuring keys was not something he wanted to do. I think a lot of people now-a-days just don't have the basic hardware set to use flight sims effectively. So, faced with either making a game he genuinely wanted to play work (not the case), or ditching a game he was merely curious with (definately the case), he chose the latter.
However, z64555 definately also srikes a chord, as I grew up without joysticks for the most part. Thus, using the keyboard and the mouse is no problem at all to me. Yet, when I had a roommate who was a pilot, I tried to get him to play with X-Plane. And that he did, but he could not tolerate the sim by flying it with the mouse, as I did most of the time. However, when we took the time to shoot each other up with the Infinity Combat Prototype, there was never a problem, and there we had to use mice and the keyboard. In the end, it's often the way the control system is set up that makes all the difference, as well as how much you want to play something (your personal adaptibility is also relevant, of course).
Finally, everyone used to make and play flight simulators. Everyone. And aeroplanes are complex flight systems which are hard to control, so you need lots of commands to manage their operation. But then, there were simpler simulation-esque programs that came out, like shooters. Suddenly, though they were quite challenging, they did not rely on vast spaces albeit with lots of controls, but small spaces with few controls. And then everyone made those. The biggest problem is that many gamers don't want to "work to play," so although they grind out those shooters to no end, a flight sim is not as interesting because the up-front labor requirement is seemingly too high. My friend that I gave a copy of FS1 to... I doubt he ever tried it again. Not only because it was not going to be a few minutes of set-up time for him, but because there were now instructions and keys to remember. The up-front labor was just too much for him to deal with.
It is possible to find a happy medium, and I think the easiest space sim that felt real to me (and can now be made much more realistic now that the the source code is out) is Starshatter. Unfortunately, SS also only really shines with a joystick. But it is proof that you can have a very happy medium between realism and simple controls. At the same time, I think that most of us find that over-simplifying controls and control schemes really takes away from the feel of the game... Thus, in the end, you're stuck with publishers, who do not want to make something that users will whine and complain about because it is too difficult, and experienced simmers who like the challenge. To meet both perspectives, somehow one must make the whole of the product desireable enough that any complexity in controls or hardware becomes acceptable to the user. Unfortunately, it's been a very long time since anyone has done that, and most users probably gawk at the concept - they've been made unfamiliar with difficult.