How far back in history is this? IME punctures are no more or less common now than when I first started driving 30+ years ago.
The repair goop is a very poor substitute for a spare wheel for next to no benefit, you don't gain any useful boot space (in all the cars I've had with repair kits, the spare wheel well is just plugged with a foam tray) and a weight saving of around 15kg on a 2 tonne car is insignificant.
I'd have thought various factors would cancel each other out when it comes to motor vehicle punctures.
On the one hand, tyres will no doubt have improved in quality. Improvements in road surfaces* may also help.
On the other hand, vehicles are heavier, our weathers are moving more to the extremes again, and there's more debris left on hard shoulders etc after collisions.
* In the past few years, road surfaces appear to have deteriorated in that the surface technology may be better, but local authorities are short on funds and so pothole repairs etc are lacking.
A lot of motors come with run flat tyres which should make it safer in the event of a puncture, but don't do much to prevent the puncture itself.
That does though, combined with £20 air compressors which run from the cigarette lighter, make spare wheels much less common.
The thing about the spare wheel to be honest is that for a long time now most of them have been space savers, so they're only really designed to run at lower speeds for a shorter distance to get to a garage. I suspect the number of 'typical car' drivers carrying full-sized spare wheels is dwindling, and those who even bother to keep them properly maintained even less so. A full-sized spare wheel is on my to-buy list, because the car is most often used for driving around the Highlands where garages and mechanics can be a long way away, especially in bad weather like snow and ice, but even I would consider just wrapping up in blankets and waiting for the RAC to rock up.