Why Use Picas?

Question

Hi, all. I'd to solicit some commentary regarding this topic, which I've wrestled with since I started doing print design 7 years ago. I can't figure out why anyone would use picas and points for measurement, other than being taught that system to begin with and clinging to it. I assume there must be a practical reason, but I can't figure it out.
Looking online, the explanation I found was that it's so much easier to do the math when using picas. To show this, they pointed out how easy it is to divide an 8.5" x 11" sheet into thirds the long way, 66 picas easily being divided by 3 into 22. This only makes sense if you assume that we always work with letter-sized sheets and always need to divide by numbers that work this easily. But what if we're working with an odd page size or need to make unusual measurements? It would seem that working in picas and points could just as easily be a complete pain as it could be convenient, depending on the project.
The other justification I've come across is that picas and points are the standard when working with newspapers and many other publications, but this doesn't argue in favor of picas as a better standard, it only favors picas as a matter of convenience and tradition. It makes me think of metric versus imperial measurements, where the U.S. continues to use the feet and inches even though the metric system appears to make more sense, the main reason seeming to be that we just can't be bothered to embrace it.
Anyway, considering that modern page layout is generally done with a computer that can easily divide inches and express fractions as decimals, is there any practical advantage to measuring in picas? So far, I can't see any reason to learn this system beyond the possibility that I may someday need to deal with someone else who uses them. So far, I've never encountered that person and even the major newspapers and magazines I've dealt with have sent their specs in inches.
Who is using this system and why? The last time I was told to use a pica was while working on my high school yearbook back in 1984! Of course, even if we'd had it then, I don't think InDesign would've run very well on our Commodore PET computers.

Answer 1

"The same can be said of any system of measurement. people use the system they are comfortable with."
That's kinda my point, I guess. I was just wondering if there was a more practical reason to use picas that I didn't understand. Mr. Benson's explanation of the 12-base system makes sense, but it assumes that division by 6, 4, 3, or 2 is more common and thus more useful, which it very well may be.
"The book I'm working on now uses a measure of 27p3 (327 points). If I try to work with that in inches, it's a most inconvenient 4.541667". "
I'm sure that's true, but I'm guessing that the book is only set up to those specs because the decision was made to work in picas. Why else would anyone choose to create a book at 4.541667"? Wouldn't it be just as easy to just decide to measure the book at 4.5" and use standard measures?
Don't misunderstand me, I'm not knocking picas or people who use them. I'm just trying to find out if there's any value in learning to use them myself and I really appreciate everyone's comments. So far, I'm not seeing any reason for me to go that way, which is also valuable to my understanding. I'm sure if you're used to using them they're far less cryptic than they appear to me!