Let's consider the effects of a world like this on the earth. First, I sure hope everyone in this situation is using cloth, because disposables are quickly going to start polluting everything around us. Water usage would probably go down some, but assuming the cloth situation, there's going to be a huge increase in how often you need to do laundry. Maybe we would develop specific sewage laundry washers for diapers. Diaper bag industries will boom, suddenly, since nobody wants to buy a new cloth every time they go to the changing room. I'd say plastic usage would drop some, since everyone would be drinking from their bottles instead of drinking from disposable water bottles. Diaper styles would become more efficient, less leaky, and higher quality, since suddenly those are very important things to people. Probably the same amount of industry dedicated to making underwear now would just be switched over to making diapers.
I hope that we're getting some renewable energy, because electric cars sound great but charging your car on coal energy kinda defeats the purpose.
The poor cows would probably see an increase in activity because suddenly everyone wants a warm baba of milk before bed, and one when getting up in the morning.
Although, honestly I see it as a double identity thing. While everyone is going to try and be in a little space as much as possible, there are times where you've got to be more adult (say, building a building, or hunting, or hiking). I think that there would still be ABDL involvements in that, but beyond everyone wearing a diaper some things wouldn't change at all, if only for safety. So there are some professions that are more ABDL (say, an office space) and some that are less (such as construction). I could also see some issues coming up in the food service industry. Probably there would be some sort of diaper cover developed specifically for food safety that you'd have to wear.
I'd like to think that'd become common courtesy to ask a loved one if they'd like a change if they have a visibly dirty diaper or they smell.
On that smell note, just think of all the diaper leaks that would occur on public transit. It would smell more like urine than it already does. Diaper littering might occur also, if it's a particularly loaded one or if you just don't want to bother disposing of it.
Although I like the idea of suddenly there being a GA/UL (Grown Adult/Underwear Lover) space opening up online just like ours here for people who like to secretly act like you do in the real world, or who just like to wear normal underwear instead of a diaper