Very true. However, a Mac Pro may be what a lot of home users may be needing. I've pitched Mac Pros over iMacs in some cases because they have the following features:
1: Server grade components -- yes, the machine is expensive, but it should last 5-10 years without issue.
2: Upgradable -- RAM, video, hard disks, hard disk interfaces, essentially everything but the CPU.
3: Reliable -- Hardware RAID turns what could be a disastrous loss of information into a dialog box that pops up saying that you need to replace one of the hard disks ASAP.
4: Adaptable -- if someone wanted to, they can just disconnect a PC they have sitting nearby, connect the Mac Pro via a VGA adapter, and continue working. Same with the keyboard and mouse (provided they are USB).
For a home user, yes, a Mac Pro is overkill. However for someone who is going to be using the machine on a daily basis for years on end, having something made to be sturdy and reliable (as opposed to cool looking) is important.