A very good question.
Well, I did some research here and found some interesting things.
First of which is that not only do men and women wear different garments traditionally, but also that they make clothes differently.
You see historically tailors were a guilded profession and they didn't let women in. Tailors taught other tailors in formal settings with defined apprenticeships, but women learned to sew from their mothers, informally (your have to remember that the printed pattern, which I talked about a few posts ago is a relatively new thing), or from taking garments apart or from observing how things were made. I think we all still do that to some extent.
It is really interesting to see how a tailor sews and how a home dressmaker sews and what the differences are. A tailor sews a hem left to right with a catch stitch (learned) the average sewer hems with a slip stitch right to left (observed). Sewers stay-stitch (low tech.) tailors tape (specialty supplies), sewers tend to use one kind of interfacing in a garments (as available), tailors use many different kinds of interior supplies (resources). Pad-stitching versus basted in interfacing - big difference in training there.
It seems to me there are many differences that could be discovered, and there are many parallels here - the chef versus the home cook for example.
Male dress, and this would include the serviceable shirt, was built to last and constructed in a sturdy way. Details that didn't go out of style, long wearing features. David Coffin in his indispensable book Shirtmaking describes these on p. 20:
Every classic dress shirt has the following elements: a one-piece, pleated or gathered back; a narrow, one- or two-piece double yoke; two front sections that overlap; flat-felled armcycle, side and underarm seams; one-piece sleeves with plackets; either barrel or French cuffs; a collar on a separate stand; and a rolled hem. That's it.
When you look at this further each part is there for a use.
The double yoke wears longer and supports the shirt details better (without adding any stiffness over the shoulder).
The front bands in a shirt are created without interfacing but by multiple layers of fabric.
Cuffs show under jackets and are distinct; cuffs can be rolled up and therefore need neat plackets that look nice on the wrong side.
Pleats at the back add ease and movement where they are really needed but preserve the slim line of the sides seams.
The separate stand lifts the collar above a tie.
The rolled hem is low bulk when tucked in and of course nothing wears like a flat-felled seam.
I mean they use those in tents.
Coffin also argues that a dart has no place in a real shirt (he says they complicate the ironing) and what does that tell you? These are classic male garments.
So I would define a shirt as a child of that history, adapted by women who were dressing for work in the male work world or who, sensibly, saw the value of a garment that was durable, seasonless and fashion permanent.
I think too that adapting the classic rectangular shirt to the female body has required some maneuvers (I think we call that fitting and that's one of the object for me here) and probably explains why curvy women always seem to me to fit into classic Lands End type shirts (and I own quite a few) with some discomfort - busts pulling, collars gaping.
I see some accommodation in this in shirt patterns with darts and more specifically in the more traditional technique incorporating princess seams that can even be flat felled.
A BTW here.
David's book is worthwhile not just as a technical manual but because it is written with charm, anecdotally, and is as much opinion as advice. Even if you never sew a shirt, IMO, it's a good read for that alone.
Now on to blouses.
I am just making this up.
If a shirt is what is described above then a blouse comes from a different tradition, less designed to be worn under a jacket and more designed to be worn alone.
To me this means more dressmaker details and less structure. Collars can be anything, and rarely if ever have a stand (we don't wear ties thank goodness), so the convertible, flat, shawl, round, peter pan, roll - well just about any collar but one with a stand is blouse defining.
There is shape.
Darts coming out of anywhere, shape in pleats or gathers, with or without a yoke, detail in the sleeves for interest, pockets for decoration not utility (what woman carries a bunch of stuff in her breast pocket - when was the last time you saw woman wearing a plastic pocket protector?), facings, interfaced, at the front, unless the blouse, like the ones in the last pattern I showed you, is back buttoning. And some can even have side zippers.
Back neck facings (which I hate and never use more on that later), and probably a real type hem.
French seams are standard finished seams. If you are using flat-felled that might by a shirt you are making.
What am I missing?
I will end this post with another vintage pattern, one that I definitely think reflects the culture of the blouse. A 1951 sleeve only pattern which, like the last one, showed the home sewer how to stretch a pattern, I am particularly in love with the turn back cuffs on views A and F.
I may end up making 20 white shirts/blouses here. And for my own purpose as a sewer I intend to mess around with all this a lot and produce both white shirts and blouses, depending on how I feel, and to just expand my tool box of skills.
I may end up making hybrid shirt/blouses some of the time.
Oh and the pattern in my button is from a current Vogue 8689.