In sharecropping (with a lot of nuances depending on the specific countries and even different regions in a same country) the landowner and the tenant were some sort of partners, both had all the interest in having a better/larger crop (or raise more cattle, etc.).
In a normal capitalistic employer/employee relationship, the employees have no particular interest in the final outcome, they are only scared of being fired if they don't meet some (often arbitrarily set) "productivity goals".
Additionally different company's have different ways of incentivizing employee "ownership". Everything from RSUs, Employee stock purchase plans, a Christmas bonus for a good year, etc.
A bonus (or other forms of incentives) are additional to the base salary.
Until you are fired (or if the company does not pay your wage anymore) your salary/wage is fixed, and you get it no matter how the company is going.
In sharecropping the year you (as a tenant) got a bad crop, you wouldn't have anything to eat, and would have basic survival problems.