Why isn't Linux more popular? I can tell you EXACTLY why.
Now, don't get me wrong, I LOVE Linux. I use it daily. I invest a lot of time in teaching people about it. But I don't bury my head in the sand.
Here's my list, it goes on for a while so bear with me. Also, I emphasize with caps... please forgive me if it grates on the senses a little.
1. "Linux is for Geeks." I hear that day in and day out. My best response is, "Download Slax Linux and burn a cd. Pop that in, and see how long it takes you to get a GUI." It's not that bad, folks. Sure, it's easier to get in and tweak majorly than Windows... but that's because it's DOCUMENTED, and that documentation is RELEASED TO THE GENERAL PUBLIC. I can do all that fun stuff in Windows too... but Linux can be used out of the box, just like Windows. STOP TELLING PEOPLE THAT LINUX IS FOR GEEKS.
2. The elitist attitude. Humble thyselves, men of Linux. It's YOUR refusal to bend down a little and help new users out that keeps them from coming. You refuse to answer simple questions, instead telling them to "read the man page." They don't even know how to use man! And, it's the most worthless, highbrow, totally assuming documentation known to God or man. You have to understand how the program works before you can use the man page to learn how the program works!
3. Big-name companies only providing RPMs. I'm serious... Give me a Slackware package any day. I track down the dependencies, I don't care. Just give me something I can USE.
4. Linux users don't speak English. They can't possibly... I've read the documentation. I write how-tos all the time about everything from finding your hard drives to recovering data from a corrupted hard drive... and I rarely get an "I don't get it." It IS possible to write your documentation in such a way that the average twelve-year-old can follow it without problems. And for crying out loud, if you're going to reference something, tell us where to find it!
5. There's no good Excel or Quickbooks alternative. Excel is probably in the top ten most used pieces of software in business, because it's so versatile. And Quickbooks is very easy to use. You just don't find that in the FOSS world.
6. Ubuntu. And here's why: It's taking thousands of great Linux users who have the potential to go out and actually get people using Linux and learning it, and shoving them in a corner finding bugs in Dapper or Breezy.
That's the start... I'm sure I can think of more when I'm not so ticked off.