I have been asked when do I wear a bra?

Well, the only way to answer this is to say that I have a set procedure:

Going into the office:

Under a white blouse or top
Under a neutral blouse or top
Under a light coloured top

Usually a white cotton bra, sometimes underwired with lace, mostly smoothe cup cotton.

Under a darker colour blouse or top I might prefer not to wear a bra at all.

Shopping or dining with friends, clubbing or at a party, maybe no bra depending on my outfit.