I can understand why I had to change my ex's light bulbs (I was tall enough to reach and she wasn't) but how come that degunking blocked pipes in her kitchen was definitely considered 'manly', but asking her to take up the hems on my new trousers while I did the degunking was considered extremely sexist? (She always laughed when I queried stuff like that!)
I would imagine (and this is all just my conjecture), that because for so long it was assumed women were good for nothing but sewing and cooking and cleaning, and because it took active campaigning, and hugely significant events (like the World Wars*) to change that, some women are left with a feeling that if a man asks them to do such a thing, it's because he thinks it's all they can do. And those tasks have perhaps been regarded as second rate by some. Whereas Manly Things, like drains and shelves, require guts and skill and so on.
It's all nonsense of course, if a woman is good at hemming trousers, and a bit squeamish about drains, and a chap is fine with drains, but finding his trousers dragging on the floor, it makes sense to exchange skills. It's just that for a long time, the hemming was seen as the 'weaker' job.
Personally, my hems are lousy, but I work with congealed gunk most days. If a chap needed a drain doing, and was handy with a needle, job done!
*I think a lot of women resented the fact that during the wars they proved themselves capable of 'manly' jobs (ie, anything other than housekeeping), but as soon as the men came home, they were expected to fit back into the home and let the men have their proper jobs back.