Older people find it easy to get for one simple reason. They don't stay for long. And if they do, they are already old. So they won't abscond or go missing to stay as illegal immigrants.

Young people are likely to stay for long, some times even tear their passports and throw away to become illegal immigrants.

Also there have been cases when elderly people from India visit the US on a B1/B2 Visa, and then work hourly wages as nannies.