It's an emotional thing. When you spend formative years in a financial condition where food expenses were significant, and free food significantly eased financial pressure on you, that reaction to free food can stick with you long after you have the financial freedom to make your own choices.
Source: finally realized that half the reason I went to technical talks that bored me was for free pizza and beer that were bad for me anyway
Source: finally realized that half the reason I went to technical talks that bored me was for free pizza and beer that were bad for me anyway