A lot of these come up with older cars like our 126 the cat converter thing for one, the air bags and many others same with our classic panda no airbags. I don't even know if these can be fitted. All i know is that if it wasn't part of the safety standard at the time of production then you can't be failed on the MOT for it. Suppose if you buy an older car you should already be aware of the lack of modern safety gadgets. We had a very in depth conversation about in the classic panda section when i bought my panda
Cat Converter I can understand, they're standard on all cars now (I think), and there is a selfless reason to them, reducing pollution. But airbags only affect the driver & passengers.