From what I've seen here in the US, it's the "I'm healthy so it can't happen to me" mentality.
In my case, I go to work, come home and, with very few exceptions, my only other destinations are gas(petrol) stations and the grocery store for food. The wife goes out even less since she works from home. We have close friends we haven't seen or even talked to since February as many of them are in the higher risk groups(many are over the age of 70, some are past 80) and are doing everything they can to stay safe. Needless to say, I can't blame them for isolating themselves as much as possible. Then again, there are others that have their groups they can't live without so they are often out and about together. Just a matter of time until they all end up on the "Covid 19 positive rosters"