It's easy to say 'if they don't notice, then clearly it's not a problem' - but it has downstream effects, like broken products, huge legal liabilities for the company including often scary handling of customer data to make it work, and morale hits as other folks pick up on things like this happening and being uncaught.
These are real, albeit currently low percentage/high risk things that happen. The more people get away with it, the higher the percentages of people who will try (people rationalize it to themselves as 'everyone else is doing it', and 'I'd be foolish to not do the same thing everyone else is'.).
The biggest issue I've seen with remote work (in practice), is it makes it really hard for a manager to see and actually understand what's happening (not just what people SAY is happening, which is rarely the same thing), and makes it easier for employees to hide things they don't want others to see. Which leads to more of everything from undiscovered-until-too-late burnout, to team members who have no idea what to do or how to do it, to opportunists grifting.
