It depends on the jurisdiction, but a lot of the "guideline amount + tracking" philosophy is driven by the law (and financial accounting).
For example, here's an except from some guidelines around the Ontario Employment Standards Act:
Employers are required to keep records of the vacation time earned since the date of hire but not taken before the start of the vacation entitlement year, the vacation time earned and vacation time taken (if any) during the vacation entitlement year (or stub period), and the balance of vacation time remaining at the end of the vacation entitlement year (or stub period).
So at least in Ontario, your employer is legally obligated to record your vacation time each year, and on demand, produce a report on it. There are also rules around when an employee has to take their vacation by, for example:
The vacation time earned with respect to a completed vacation entitlement year or a stub period must be taken within 10 months following the completion of the vacation entitlement year or stub period. The employer has the right to schedule vacation as well as an obligation to ensure the vacation time is scheduled and taken before the end of that ten-month period.
Since Ontario is also a jurisdiction with legally-mandated vacation time, at any point in time the vacation that an employee has accrued but not yet taken (or has rolled over from another year) should also be recorded as a liability on a company's books, since it could be forced to pay out the equivalent vacation pay (if the employee leaves, for example). The obvious way to get around this - and I've seen it done in a few places - is to pay everyone their full statutory vacation pay every year and then not count the vacation days taken, but that's basically giving everyone a 4% raise, and isn't even an option in some jurisdictions.
All of this is to say that unlimited and untracked vacations may not even be a legal option everywhere, regardless of what we think of them.
I doubt unlimited vacation is legal anywhere but the United States where our labor and employee wellness laws are much weaker than in the rest of the developed world.
For example, here's an except from some guidelines around the Ontario Employment Standards Act:
Employers are required to keep records of the vacation time earned since the date of hire but not taken before the start of the vacation entitlement year, the vacation time earned and vacation time taken (if any) during the vacation entitlement year (or stub period), and the balance of vacation time remaining at the end of the vacation entitlement year (or stub period).
So at least in Ontario, your employer is legally obligated to record your vacation time each year, and on demand, produce a report on it. There are also rules around when an employee has to take their vacation by, for example:
The vacation time earned with respect to a completed vacation entitlement year or a stub period must be taken within 10 months following the completion of the vacation entitlement year or stub period. The employer has the right to schedule vacation as well as an obligation to ensure the vacation time is scheduled and taken before the end of that ten-month period.
Since Ontario is also a jurisdiction with legally-mandated vacation time, at any point in time the vacation that an employee has accrued but not yet taken (or has rolled over from another year) should also be recorded as a liability on a company's books, since it could be forced to pay out the equivalent vacation pay (if the employee leaves, for example). The obvious way to get around this - and I've seen it done in a few places - is to pay everyone their full statutory vacation pay every year and then not count the vacation days taken, but that's basically giving everyone a 4% raise, and isn't even an option in some jurisdictions.
All of this is to say that unlimited and untracked vacations may not even be a legal option everywhere, regardless of what we think of them.