Why do they need that extra (depending on where you are) 2 - 4"? 11" isn’t good enough?
(honestly, I’m not sure)
Have you ever READ a legal document? Isn’t law all about how to write long documents that make no sense?
I don’t remember if it was said to be the reason for the size, but in school we were told that one hand-written legal pad sheet was a reasonable approximation of a double-spaced typed page. Seemed to work for me.
Cecil has a slight error in that column, although I can’t shed much light on the legal size question.
Industrial cut paper sizes are more likely to be 17.5 x 22.5 inches, not 17 x 22 as Cecil says. When sheet paper is cut (as opposed to cutting from a roll), it is usually “double cut,” that is, all edges are trimmed off, then the final size is cut out. While that seems like a waste, it cuts off just enough to remove damage from the most vulnerable part, the edge. Edge damage in commercial printing makes the print job look bad, and feeding paper with edge damage thru presses isn’t a good idea, either.
17.5 x 22.5 becomes (4) 8.5 x 11 plus trimmings.
So large stacks of paper are shipped to the end destination, typically on pallets, then cut to size either just before printing and/or just after.
And the slivers that are trimmed off can be recycled into shredded packing material or other reuses, so it doesn’t always end up in the dumpster.
FWIW, I’ve been an attorney for about 7 years, and I’ve never used legal size paper for anything, nor can I recall ever receiving a document on legal size paper. Maybe it’s used in other practice areas or other regions, but not mine.
I think when I bought my house there may have been a doc or two that was legal size, but that’s the only time I’ve ever seen it used. Wonder if it’s going the way of the dodo.
We can only hope it becomes obsolete. It seems to be fairly common in my neck of the woods. I just refi’d my house and came home with an entire folder full of legal size documents. Now exactly where will I file those…?
I’ve been a lawyer since the last millennium, and I am pleased to say that legal size is falling out of favor. I still see it used in real estate deals. I try to avoid using it whenever possible. It’s inconvenient to have to have some on hand, to have some papers hanging out of the bottom of the file getting a lot more wear, etc.
When I started, Mid-1980s-- it was being phased out. Some courts still required/allowed it. I don’t see it anywhere anymore, but imagine there could be pockets of “old school” pleadings still around.
Legal length is pretty well a dead horse out here. The state and federal courts require letter size. The recorder of deeds discourages legal length. There might be an occasional obsolete fill-in-the-blanks legal length form floating around but that is about it.
All my 40 year old file cabinets are for legal length so I use legal size file folders – it leaves a space at the bottom for phone numbers and the like.
You will, however, have to pry my legal length yellow pad from my cold dead hands.
We use legal and ledger a fair bit at my engineering firm for printing out small runs of small sets of drawings.
8½ by 14 is the standard at my work for printing drawings and other documents. We rarely save them though, most end up in recycling box by the end of the day.
Unless you’re the Maricopa county Arizona recorder of deeds where they prefer legal sized documents be submitted for recording for some reason.
The only real estate related docs that we still produce that are always on legal sized paper are HUD1 statements, but that’s just because they’re just too busy and detailed to hope to be legiable on letter sized paper.
I saw some when we bought our place which gave me one possibility. We had to initial everything. Maybe they add some room so you aren’t signing your X over something important?
My only other thought would be if they left a gap at the top. When you have a stack of papers held together at the top (not spiral bound) and are flipping through them, the farther “down” you go the harder it is to read the top of the paper. (I’m mostly thinking of medical files because my doctor’s file on me is about 8 1/2" thick).
Does either sound credible?
Yep, at my closing was the last place I actually remeber seeing it used. That and the banks papers. It’s almost like they want you to feel out of place in there preseance because they require paperwork so important that it needs to be larger than life.
I use it at work sometimes to print out drawings and spreadsheets so that I can actually read those damn little cells or actually view the whole sheet on one page in a meeting. Never fails that some smartass in the group comments about the large scale printout while typing on his laptop. Usually some cocky youngun with good eyesight; if had a cane I’d smake them all. 
My understanding is that the extra length was originally used for notaries’ seals and that kind of thing.
When I practiced law in the 1990s, we no longer produced documents on legal-sized paper, but all of our binders, files, and cabinets were still legal-sized. Every few months there was another notice about some court, agency, or other body that was discontinuing legal sizes.
Most people still used canary yellow legal-sized pads for taking notes on though.
If you’re using an illegal paper size, we’re going to have to report you to the authorities.
Come on, people! Get with the programme and use A4 like everyone else, and let’s have less confusion!
Those lawyers had better be using legal pads to take your statements though. 
What exactly is the confusion? Do we also have to eat your favourite flavour of ice cream and wear clothes in your preferred style too?