When I first came to Korea back in 2005 I was surprised to see women, and some men, using umbrellas to shade themselves from the sun.
After having lived here for five plus years I now understand that there are multiple reasons for needing ‘sunbrellas.’
Some of these include,
1) avoiding heat exhaustion or heat stroke
2) not wanting to wear a hat that might mess up your hair
3) the ‘ajumma visor’ is nowhere near as nice looking, LOL!
4) the sunbrella also protects your arms a little
I’m sure there are more reasons but these are some good examples.