Well it can be due to hygiene or just excess sweat that particular day. It can even be from medications or an infection, etc. Sometimes it isn't controllable. I don't think I've ever heard of a vagina having a bad scent naturally. I've heard of women having unpleasant odors during their menstrual cycle, but it's probably not as bad as they think. I rarely have any scent. You CAN smell your own vagina. If it has a strong enough smell that a partner would notice it during sex then you would smell it while going to use the restroom or by swiping your hand down there and sniffing. Lol. I've had a blood/metallic smell when I had periods. Gross. Sorry. Even certain bath products can cause odor to women who might be sensitive to that sort of thing. UTI's can cause odor. I doubt any woman has an unpleasant odor after showering or every single day. I shower daily and keep a good check on myself. I like that my scent is hardly detectable besides during or fter intercourse. Every person's privates put off a scent, not an odor, just their own natural scent during sexual activity. It may be the person who just doesn't feel comfortable with being close to vaginas that cause them to think the smell is worse than what it is? I don't know.
Now I don't get why some men think penis cannot have odors but vaginas can. Penises can have just as bad of an odor as a vagina can. I've smelled it before! Also men tend to sweat more and that causes you to be more at risk for odor.
I didn't think of this until now, but if someone truly has a bad odor it could be due to a lot of hair. Hair down there gets sweaty, it's not able to breathe much and it harbors bacteria. That is one reason I do not allow hair. I don't like the idea of bad bacteria. Some bacteria is necessary to have a healthy cooter, but hair can cause a person to be more susceptible to odor.