Women may assume other women have menstrual products and painkillers

If you are a woman (or others think you are a woman), women may occasionally ask you for pads, tampons, or over-the-counter painkillers like ibuprofen.

This is because most women menstruate, and periods aren’t always entirely predictable. People who menstruate can end up bleeding through their pants if they get their period unexpectedly and don’t have a pad/tampon. Pads and tampons are often not readily available (most bathrooms don’t have vending machines anymore).

Often, the only way to get a pad/tampon quickly is to borrow one from someone else who uses them. Since most women menstruate, often the best option can be to discretely ask a woman within a certain age range if she has one you can use. Since most women have been in this situation, most women are willing to share occasionally (with the expectation that others will share if they need them). So, if people think that you are a woman, they’re likely to assume that you have and are willing to share. 

Similarly, many women have migraines or cramps, and carry ibuprofen or other over-the-counter painkillers in order to deal with it. For whatever reason, it is often not readily available (office vending machines occasionally have it, but not usually). Being caught without ibuprofen when you need it is really miserable — and most women who experience menstrual pain have been in that situation and wouldn’t wish it on anyone else. 

So, it’s generally socially acceptable for women to ask each other for ibuprofen, and most women are willing to share from time to time. (So long as it’s not a situation where someone is regularly mooching off of them and not reciprocating.)

Tl;dr Most women of a certain age menstruate, and most people who menstruate are occasionally caught without menstruation-related things they need. (Eg: pads, tampons, ibuprofen). Often these things are not readily available, so most women share with each other from time to time. If you’re a woman or others assume you’re a woman, they may also assume that you have these things.