Because they are expensive pieces of crap.
The haters were quick to jump on this one. Why do you want one? Because they are the classic American military pistol that is just as good a choice for carry today as it was when designed over a hundred years ago. Shooting a 1911 is like shaking hands with Audie Murphy. The guns are well balanced and can have triggers that are almost as good as it gets. Even a stock, low budget gun has a great trigger when compared to most modern DA/SA guns.
There are a lot of myths concerning the 1911. One is that you have to buy an expensive one to get a reliable one. Not true. Just do your homework and you can find a solid gun for well under $800. Even the consumer grade 1911s (Remington, Springer Mil-Spec, Ruger) are great guns. Another myth is that you have to put money into parts to keep them running. Simply not true.
One reason to buy one is that it's the only handgun in existence to have shot down a Japanese Zero. That happened in the western Pacific when a Zero pilot was shooting as parachuting American airman. One pretended to be dead and when the pilot did a slow fly by to observe his handy work, the airman lifted his 1911 and took a shot. The Zero crashed with the pilot being ejected. He had a single bullet hole in his head.
1911s are a fantastic gun and most people would enjoy having one in their collection. We live in a great time as there are many choices out there for a 1911 buyer. One of my favorites is the new CZ 1911A1. It's a fantastic shooter right out of the box. I've got north of 800 rounds through mine since getting it in October and there has not been a single hiccup. I had a Glock 19 that could not get through a magazine without jamming until it was broken in.