The mere-exposure effect is a psychological phenomenon by which people tend to develop a preference for things merely because they are familiar with them. In social psychology, this effect is sometimes called the familiarity principle.

Whenever someone on the Internet says "things used to be so much better in my day" or "why did they have to change change X, it was already perfect", this effect is probably the reason.

I've noticed this attitude most commonly in music communities, where some older listeners never even try to understand current trends in music. Though software communities are not immune to this either.