ROFLMAO
if we could speak somewhat authoritatively on the subject, i'm sure we
could do a culture class on it. the problem is we're just as baffled as you by it.
i've asked a lot of japanese people about it (and as you probably already know, it's not strange for them to see it). the closest thing to an answer i've gotten is "i dunno,
that's just what old ladies do. " and as this is japan and sometimes, well, you just do things a certain way cuz that's how it is...
probably, the best person to ask would be an old person's hair dresser.