Because the 1911 is manufactured by just about every manufacturer worth mentioning, and several that aren't.
Because each one is just a bit different...and some of them are really incredible.
Because 1911s come in barrel lengths from three to five (and even six) inches....and with frames made of carbon steel, stainless steel, aluminum alloy, Scandium alloy. In chamberings from 9mm to .38 Super to .40S&W to 10mm to .45acp to .50GI. Manufactured in the Phillippines and Turkey, Brazil, multiple locations in the US.
Because people like Ed Brown, Bill Wilson, and Les Baer build really nice semi-custom 1911s...and then there are the truly custom guys that most of us have never heard of.
Because the 1911 aftermarket will support your every desire. You can buy any and every single piece of a 1911 from multiple sources....often in multiple configurations.
Yes, the world of 1911s truly stretches far and wide. Your imagination and your budget are the only true constraints.
If you like 1911s, there has never been a better time to be alive.
I have only owned about 25 1911s in the last 25 years (almost exactly the same number of S&W revolvers, although in a shorter time frame).
I cannot afford to own them all at once, so I am a serial owner. Owning a few at once is fine. If I find one I want, I sell one I am not enjoying....enough.
This helps me to appreciate each one I own. I either carry it or shoot it regularly...or else it is gone.
I read BC's (or BAC, depending on where you read) posts on his 60+ 1911s with a small degree of envy...but only a small degree.
Since I have neither the money or the years remaining on this Earth to make too many (more) ill-advised purchases, I am in his debt, and read of his exploits with fascination.
I have owned a bunch of "other" handguns as well, and nearly all of them are now residing elsewhere.
Unless you are a man of exceptional means, you will probably never own multiple beautiful beachfront homes, or a car collection like Jay Leno's. You will probably never have multiple supermodels wives (and may God help you if you do).
On the other hand, owning several very nice, very different 1911s is very do-able for an average gun owner.
If I were to try to boil it all down to one sentence:
There are just too many great 1911s out there to be satisfied with just one.
Happy hunting.