@Z2JeAjG-2dcu - You should look into labor laws, they're fascinating.
EDS, HP, HPE and others have fallen foul of exactly what you state in the past - you cannot measure a salaried employee based on a time card. The minute you require them to clock in/clock out or log in, log out etc, they become 'hourly' employees, and are entitled to overtime and other compensations. Back in the days when we had contracts, they could specify things like start times and end times....and you consented to those when you signed the contract. I haven't seen one of those (at least in the US) for 20+ years.
Salaried employees get the same pay regardless of hours worked. The company doesn't care if you work 60+ hours, they don't have to pay any more. For them, it's basically free work. If the employee is consistently performing their tasks in less than 40, then that's up to management to determine if the compensation being paid for those tasks is acceptable or not. They can then add more responsibility/deliverables, and the employee can then decide if the remuneration is still acceptable.
No one is 'cheating the company' - if anything, it's simply representative of the inept management this company has displayed for years - in most cases, your manager has no idea what you do, has no way to reward you for going above and beyond, and frankly is little use other than to be a sympathetic ear when you have an issue...even though they probably can't do anything about whatever issue you have anyway. As long as you put 40 hours on your timesheet, they can check the box and their boss doesn't b--ch at them.