Yes but now they can't change because the first one to do this becomes uncompetitive, the only way to introduce this in a fair way that otherwise maintains market competition is to introduce a rule that applies to all the companies in the market that says you must offer paid sick leave.

Edit: A more extreme example; there is a rule that says airlines mustn't make pilots work more than a certain number of hours without a rest period. This rule applies to all airlines. This rule was introduced to reduce the number of planes crashed by tired pilots.