I got fascinated by this when I saw mention of this elsewhere. I'll agree that getting sturdy casters at a reasonable price was definitely part of the problem. As the linked wikipedia article reminded me, 20-odd years ago you'd still come across wonky casters on very expensive supermarket trolleys.
I think like the bicycle, it was just combination of factors preventing adoption - and once these had all moved, it was an obvious improvement.
e.g.
The luggage you put the wheel on. My distant memories of family suitcases weren't rigid. Deformable cloth over a flexible outer band of some type.
First ones with wheels I saw just had them on one bottom corner and a drag handle on the opposite top corner. Where f'in vile to use, as the whole thing would flex as you pulled (Toppling and attempting to break your wrist).
They only really became 'good' when we got rigid luggage (carry on bag with extendable handle or rigid-shell case like Samsonite).
But another reason is that previously "You didn't have to move it yourself"
In 'the golden age' a porter would put your trunk/case on a wheelbarrow for you. Then these transformed into 'rows of luggage carts in the airport'. Then as the decline continued 'rent-able luggage carts, you didn't have local-change for'... and at this point lack of service for your bag, crossed our ability to make wheeled luggage - and we all bought it.
But early wheeled luggage didn't have casters, just straight wheels. And those wheeled carts that you see old people dragging home from the supermarket (in some cities) existed long before -- metal frame, sagging canvas bag, works great.
There are lots of other factors though. One was buildings with lots of smooth floors & no stairs, which IIRC was partly about designing to be wheelchair-friendly, and partly about luggage carts.
Another as you say was flying becoming less of an elite thing -- the private jet people today sure as hell don't muscle their own luggage anywhere, so theirs just has to look good in the hotel room.
Another was just savvy marketing: again IIRC, the breakthrough came from marketing them heavily to pilots first, cool people in smart uniforms (who did not have porters) breezing along with smart leather bags. Precisely to break the image of old people dragging their potatoes home.
Other thing I'd meant to mention, was that the territory of "wheeled luggage" has expanded. Previously maybe at an airport you'd haul your luggage to a car at the kerb that will take you to your destination.
Modern airport usually has some public transport that takes you into town, and from there you get further transport to where you wish to go.
i.e. Having your luggage be less of a burden opens up your choices.
I live in a university town with a lot of foreign students. It's now entirely normal for me to see one 'herding' (for want of a better word) a flock of cases quite successfully down the pavement infront of me.
I think like the bicycle, it was just combination of factors preventing adoption - and once these had all moved, it was an obvious improvement.
e.g. The luggage you put the wheel on. My distant memories of family suitcases weren't rigid. Deformable cloth over a flexible outer band of some type. First ones with wheels I saw just had them on one bottom corner and a drag handle on the opposite top corner. Where f'in vile to use, as the whole thing would flex as you pulled (Toppling and attempting to break your wrist). They only really became 'good' when we got rigid luggage (carry on bag with extendable handle or rigid-shell case like Samsonite).
But another reason is that previously "You didn't have to move it yourself" In 'the golden age' a porter would put your trunk/case on a wheelbarrow for you. Then these transformed into 'rows of luggage carts in the airport'. Then as the decline continued 'rent-able luggage carts, you didn't have local-change for'... and at this point lack of service for your bag, crossed our ability to make wheeled luggage - and we all bought it.