Not that people aren't shit but I don't think the communication has been helped by our "ooh a terrible terrible lockdown, I can only go out for a run once a day. And to the shops." I think a lot of people mistakenly think that's the same as quarantine.
It isn't. People arriving from abroad that are required to self isolate aren't allowed to leave their home.
There was some survey somewhere that suggested about 20% of people follow the rules when required to self isolate for any reason.