I suspect this is related to the phenomenon that people often quite strongly need to justify their purchasing decisions, leading to fanboism (I know that free

I suspect this is related to the phenomenon that people often quite strongly need to justify their purchasing decisions, leading to fanboism (I know that free systems also have fanboys but I think there is a difference in the type). So if people made a monetary investment they have the emotional need to justify to themselves and others that they made a good decision (hence you talk positively about that purchase), however somehow when they use something free, people don't feel that emotional need.