HillyN I am 80 and am yet to have a problem with clothes fitting me. No I am not willow thin, but because my hips and ribcage are very close together, I have never had a waist and this is a problem I have contended with all my adult life, not just since I got older.
However, it does bring up another reason older women have difficulties with clothes and that is quite simply that so many of us are overweight. 70% of women over 60 are obese, compared with less than 50% of younger women. But overweight younger women have the same problems as overweight older women and they seem to be able to find clothes.
I agree with Poppyred over people wearing clothes that are too small, mainly because they do not want admit how big they are - and we already have clothes sizes that are considerably larger than those sizes were 50 years ago.
Very few people have perfect figures, we have naturally high waists, low waists, longer than average arms and legs, short necks, big busts, whatever, we adjust to them when we are young, it is just we change a bit as we get older and need to readjust again.