A cow's value is based solely on its milk. If it stops producing milk, it stops having value, and is killed. The proletariat's value is based solely on their labor. If they stop laboring, they stop having value, and are left to starve.
If a chicken lays more eggs, it doesn't get a bigger coop. The farmer decides how much the chicken is given, and that amount is almost always far less than the value what they produce. If the proletariat produces more value, they don't get paid more. The bourgeoisie decides how much the proletariat is paid, and that amount is almost always far less than the value of what they produce.
When a donkey can no longer cart for the farmer after spending its entire life carting, the farmer may generously put it out to pasture, and it will finally get to enjoy the comparatively tiny portion of existence it has remaining in peace. When the proletariat can no longer labor for the bourgeoisie after spending their entire life laboring, the bourgeoisie may generously let them retire, and they will finally get to enjoy the comparatively tiny portion of existence they have remaining in peace.
In principle, the bourgeoisie views the proletariat the same way that a farmer views his animals. Our lives are only worth having if they are spent in their service, our labor is stolen so that they may turn a profit, and those of us lucky enough to one day leave the farm of capitalism are only able to because every drop of value has been squeezed out of us by them from youth to venerability. Fighting against this system is the most sensible thing that a victim of it can do