A large or rim puncture flat
A large or rim puncture flat cannot be fixed by goo and so you'll be stranded, a mini spare will allow anyone to limp home regardless of the damage to the original tire. I hear cars with LSD differentials can be damaged by the mini tire so a rear flat requires moving one of the front tires to the back, and putting the spare on the front. Run flats are only good for about 50mi at 50 mph, then it starts to deteriorate quickly. After 50 mi, it won't be safe to drive at all, I know it happened to me, at about 60 mi it starts grinding on the rim and will damage the wheel, regardless once a run flat is run flat the tire has to changed, a huge expense. I don't know if makers tried to kill the spare due to its cost. Most new wireless car keys cost more. Aftermarket mini spares run $100 tops, a full size spare with el cheapo rim is about the same. I think it was just bad engineering, that goo, if it works, also expires, so needs periodic changing. Why fix what ain't broke? I guess car makers thought they went from full sized, to mini size, to glue, all was well?