That class of mobility scooter using super obese people you're talking about starting popping up about 20 years ago and really became noticeable about 10 years ago [1]. If the rest of the world is several decades years behind the US, then you wouldn't expect to see very many people in this class for another 20 years or so.

[1] Though it isn't really that common. It's just that super obese people are very noticeable, so it feels like their are more people in this category than there really are.