Without laws and regulations it is up to you to negotiate. With the laws and regulations it is already negotiated for you, you have no choice but to accept part of your compensation in vacation/sick days rather than in hourly wage.
And without the laws and regulations I have no choice but to accept sod all holiday time because employers won't budge on the issue. The average person's negotiating power is minuscule compared to a big company.
Before health and safety laws workers got killed on the job all the time, and the attitude was largely "there's lots of desperate workers, they can be easily replaced". If a safe working environment was beyond the power of the little people to negotiate, what chance a less serious matter like holidays?