You’d be right.
Some people like it though, and since it is such a popular product, why do they like it?

Well, I’m a lazy man, so I’ll go with another ordered list to explain:

1. Support, when you pay for it, you get it. I’ve never had to use it, but it is probably pretty good. They’ll even sell you a book if you can’t figure it out. Bugzilla obviously only has free support and possibly somebody will sell you some if you try hard. Not really the same thing. You can also buy FogBugz without support though, which is hilarious when they’re charging a thousand dollars for ten developers.
2. Joel Spolsky. He writes a blog called Joel on Software, you’ve probably heard of it. Some people trust what he makes because of it. I certainly like some of the ideas he espouses in that blog. He also has some books out, et cetera. This all takes you around back to his software if you are in a position to make purchasing decisions for your company.
3. Consistent form and functionality. If you’ve ever used Gnome, then tried a newer major version, you’ll notice that they contain major changes to both form and functionality. This isn’t even half as bad as some other open-source projects, if you’re lucky enough to even get updates…
4. Works pretty much out of the box on three platforms, as long as you’ve paid for each or are willing to go through the support hoops (gotta have a paid support contract to switch, too.)
5. FogBugz Screenshot, yeah it isn’t really perfect, but if it works, it works.
6. Security through obscurity, FogBugz is not open-source software, therefore it is less likely to have security bugz found by h4x0rz. Which is also why RMS is holding that sign:

There are lots of good reasons to not like Joel Spolsky’s take on web bug management tools, and while the above screenshot is not entirely valid, other good reasons do exist:

1. If you add one user/seat over your paid limit, it (until you delete a user or buy more user licenses) disables every user. It even logs users out, and then taunts them with a message to buy more licenses when the user tries to log in again. Real friendly like.
2. Not one free test case tool works with FogBugz beyond linking to the bugs. Obviously there are significant barriers to them doing so, but seeing as many of them work with Bugzilla, we can count this against FogBugz.
3. While the screenshot tool depicted failing above is good when it works, when it doesn’t, it fails miserably and distracts you from the task at hand – reporting bugs with your defect tracking softare. I’ve had it display the login page for FogBugz (with the latest version) numerous times.
4. (This is wrong, see the comments, thanks for the correction) At least with open-source software I can have a chance at fixing the bugs myself.
5. You’re not in control of the software at all. They recently launched their major upgrade with a movie depicting how awesomely web 2.0 they are. Great guys, you’ve got ajax and a few usability improvements, did this really neccessitate a major number increase?
6. Go search for “bugzilla” on Google. Go on, I’ll wait…
7. Okay, back with me? Note the ad if you don’t have customize google installed. Yeah, FogBugz is advertising on Google AdWords with anti-Bugzilla propaganda. Real professional.
8. To add something to a case it takes two clicks. You have to click on a bug, and then click again to edit.