People can always use them (provided they are someone who wears pajamas, but if it’s a family member, you probably know that already, and if it isn’t a close family member or close friend, why are you giving them pajamas?).
In 2004, ABC News conducted [pdf] a telephone poll of 1,501 American adults and found that, contrary to my theory, a nightgown or pajamas were the most common sleepwear option. But just a slight majority of women chose this option, and only 13 percent of men did.
Hardly any women slept in “underwear,” according to this survey, and given some women’s attitudes toward certain of their unmentionables — “off the moment I get home,” I’ve heard several times with regard to one particular garment — I can’t say as I blame them.
At the other end of the continuum, you have people like me who have owned no pajamas in half a century.