Couple of things from my own experience - so far we've managed to avoid cars without spare wheels. In one case it was an optional extra at no cost (the gunk kit fitted in the wheel well in the boot, it was a straight swap), in another case it was an optional extra at some cost, but "thrown in" for various reasons - and this on a second-hand car!
I would agree that the most common puncture is probably a nail in the tread, and that this can be worked around with a can of gunk. A nail in the tread can often be plugged by a tyre centre at considerably less cost than a new tyre and I believe (but don't know) that current gunks can be washed out of a tyre, so it isn't necessarily the case that using gunk ruins a tyre. However I have had quite a lot of punctures over the years and a good number of them would not have been amenable to gunk. Gunk can't deal with a slit, particularly in the sidewall of a tyre. The last puncture on my own car was a rip along the sidewall when a vehicle coming the other way in a narrow lane forced me too far over and I hit a stone - there is usually room to pass at this point, but he was coming too fast around a bend and couldn't get back to his side of the road, or maybe he didn't want to risk scratching his paint. My wife's last puncture was a twig in a forestry car park. Both required new tyres and could not have been fixed by gunk, but in both cases the spare wheel allowed us to drive away.
I think there are several reasons for removing the spare tyre, on the part of the car manufacturer. First, a spare wheel and tyre probably costs more than a can of gunk - even the gunk-plus-pump systems seen in some cars. Secondly, it will save some weight, which will make a (very small) difference to the fuel efficiency of the car. Thirdly, and particularly for smaller cars, it will save space, meaning a slightly larger boot - some cars such as the original Smart car probably don't have room for a spare tyre of any description anyway. Lastly, many people wouldn't know where to begin with changing a wheel and would call in the AA / RAC / Green Flag even if they did have a spare. I'm not sure that this last one is a real argument as it's likely such people would also balk at using a can of gunk, but it's a possibility.
One of the reasons (though to be fair, not the main one) I'm still holding off getting an electric car is that they all seem to have some functionality built in to a smartphone app. Surely this isn't actually necessary? Surely it's not impossible to build a modern, efficient electric car with knobs, dials and switches? And a physical key?
M.
