It is when I was a newbie here and I have to buy something that bitcoin is the only payment on that site. So, I asked a friend if he knows someone that sells bitcoin and luckily he knows one. Then, I PM that someone and ask how much is his price in bitcoin and I was so happy because it is not that expensive. To be honest I've got a discount because that someone that I bought my bitcoin is in the same church as mine.
i normally use to buy bitcoin for investing in other sites, specially in alt coins and in gambling, for the first when i heard about bitcoin from a friend it really fell to me interesting as i already did work in stock exchange therefore it was not so difficult to me to learn about investing bitcoin and get benefit from it.