So few people will change their own flats nowadays that the eu is considering removing the requirement to carry a spare.
Uniquely Spain requires you to have a hi-vis vest in the car in case you need to change a tire, this definitely makes sense and I'm betting most people here carry one.

Not sure about the extinguisher, given the rarity of accidental car fires and that most of them occur on freeways/major roads I think the risk of people being hurt trying to fight them (by the fire or traffic) probably outweighs the benefit.
Nevermind how you would enforce it when so many people refuse to even wear seatbelts.