I seem to have a good few of these, As a result, I don't consider them actual friends. E.g. I know someone for 20 years, have spent a lot of time with him, socialised, had long conversations etc. But it became apparent that I was sharing considerably more information than he was. I wouldn't expect someone to disclose how much money they have in their bank account or if they're having difficulties getting their cock hard. However, if someone got married, I would expect to be told and not have it treated like some big secret as happened in this case.
Another example, a person I've known for 20 years and have had many conversations about careers and life generally. I would have mentioned my parents' occupations on numerous occasions. Yet only recently did this person disclose that their father had the same occupation as my mother.
Another example, someone who gets work done on his house regularly but getting info out of him on who did the work is like getting blood out of a stone. I assume that the strategy here is to "hoard" good tradesmen for himself, as if he tells other people, those tradesmen will get too busy.
Numerous others too. Is this part of Irish culture, being outwardly friendly but friendships are shallow. Is it more prevalent in certain parts of the country e.g. border and west. Are people insecure and paranoid about giving away information? Whatever they're at it, doesn't seem to work that well for them, nobody I know who does this is a high achiever with a stellar career. Some would have benefitted from nepotism though, cute hoors basically.