Fair point, but it's not just the buggy. There's all the cleaning equipment, nappies, food, change of clothes, etc. Plus, it's nice to have an excuse to keep buying new cars 
yeah know they have loads of stuff to take with them, it just seems a bit bonkers to change a car you like for a more expensive one you miahg tnot like just to accomodate a some stuff that you could easily cut back in size (although if your mrs is anything like mine it may take some explaining).
If on the other hand the finances aren't an issue and you fancy a change of car anyway it makes sense to buy a bigger one.
It just amases me the number of times I've known friends take out massive HP agreements on big new cars so the buggie will fit in the boot and then complain they're skint. My mum managed with 2 kids and all their stuff in a MKI Fiesta.
nick