Sure, functional and aesthetic improvements were certainly part of it, but don't think that having a proprietary connector that had to be licensed to make accessories had nothing to do with it.
Proprietary didnt mean squat for like 3 different generations of consoles. Being proprietary wasnt the main issue of those times, like it is today. $$$
They're a little rougher to plug and unplug partly because it's a tight plastic on plastic fit. It's not so bad with normal metal shelled d-subs, but they don't pop off either.
They are tighter, by choice. Dsub intentionally have screw-downs, to keep connectors from coming loose. Dsubs thin metal shell is also a weakness... as any small drop, and the metal will bend out out shape, making it impossible to insert the connectors together, without bending it back precisely.
Of course, the reason for the flimbsy metal, is because they are not designed to be constantly plugged / unplugged, and swung around, dropped...etc... like a typical game controller.
Theres always a reason for a certain design. Its pretty easy to understand, if you actually take the time to consider all the aspects.
I'm not arguing that an edge connector might be a little easier, but you're way overexaggerating the difficulty of using a d-sub.
A littler easier??!! Again, Proove it. You are so gung ho about how easy it is... then show up a working video of it sliding in and out freely, consecutivly,
for 60 seconds of flawless in and out. And also, document the time it takes you to actually Make such an accurate fail-proof connection.
A large PCB edge connector, has like a full MM worth of play in any axis. The conenctor will still be guided in without much trouble, even with a little slop. But a Dsub has almost Zero tolerance. They are super tight to slide on. Many a day, Ive had difficulty trying to insert one blindly (by feel alone) into a monitor... yet, I could easily insert a PCB edge connector without issue.
The smaller and tighter the tolerances, the higher accuracy you will need in making an exact positional matiing. The differece between the Dsub and a ISA card, is not like 1 to 4. Its like 1 to 100, in the scale of magnitudes of difficulty in precision alignments.
If your control panel had wooden guides, and one of the guides wore down a mere 1/2 a mm.. the dsub connect, that you spend hours and hours trying to precisly align... would fail to connect.
Not only do you have to worry about the x and y precision, ... but also, in addition to wear, you must consider any twisting, sliding, warping, shrinkage / growth..etc. From moisture, to heat / cold... as well as structural shifting / density issues. (ever notice that certain doors in your house get tigher or looser, depending on the season? or house shifing..)
A similar issue is found in gears. If you use a very fine tooth gear, it requires very precise alignments. If your off by a fraction, gears will skip and wear, and shear off. Larger gears will be easier to work with, as you can be off by as much as a mm or more, and still make good enough connection to avoid wear and slippage. If you would like to see proof of this, check out a real Arkanoid spinner. Almost all of the old arkanoid spinners are toasted... and do not work correctly. But yet, you can easily find large geared pedal sets that were made before Arkanoid, that were used and played more often... that still work flawlessly today. No gear destruction at all.
Don't mind X2. The last time this conversation came up he had "the perfect solution", was requested pics, and never delivered. He's good at 2 things: napkin engineering, and blowing smoke. Not necessarily in that order either…
To date, Ive built working Starwars and Super Hangon controllers, without even use of a simple sketch. Its also a few of the reasons why I know more about materials and tolernaces. Because of actual physical experience, with setbacks from failures of things actually built.. and or arcade / pinball related things that failed, that I repaired.
This isnt about the perfect solution either. This is about what is easier, and actually managable, by a non cnc / machinist. As well as far more robust than hand-disconnecting cables.