This kind of thing about 'bad' people being deliberately nasty - even murder or child abuse) - they may still be being the best person they can.
It doesn't make their behaviour acceptable in anyway shape or form. BUT for whatever reason they don't know or believe the 'norms' apply to them or even don't care - but it isn't a choice not to care.
People who are lazy - they don't actually make the choice to be 'lazy'. They choose on occasion, not to be lazy because they know being lazy is not acceptable but their default is 'lazy' and not being lazy at any given time is a choice - being innately lazy isn't - some people are better than others at choosing not to be.
Just the same as another person's default is to constantly be on the move. They may choose to, for example, sit by the pool on holiday and read a book, within half an hour or so, they are getting fidgety and can't sit still for much longer.
It's as hard for an 'active' person to sit still as it is for a lazy person to be active. Often the lazy person is the one who is criticised but they are actually putting in more effort than the active one because 'active is good' so they just be who they are. They lazy person overcomes their natural way anything from 1 to 1000.s of times a day.
The person not indicating may be distracted - or not indicating may be a habit. They may be arrogant and think that it isn't necessary for them - but even that is an inherent or learned behaviour.
Lots of behaviour isn't acceptable and I am not excusing it but it's rarely a decision to be deliberately nasty and when it is, even that is without their control - they feel justified because of what has happened to them or they were born without a conscience or it's what they have grown up with and believe that everyone else behaves in the same way or some other reason that we don't know.