Why is the history of all hitherto existing society a history of class struggles ?
Cause necessity is the mother of invention. Cause necessity is the mother of invention.
Material, biological necessity, physiological need. We are still in the Realm of Necessity !
Ever since there has been a material surplus, there have been those who exploit others by living off the surplus created by other's labour.
The surplus is coerced from them under threat of deprivation of physiological life, threat to a physiological necessity.
The surplus fulfills the biological necessities of the exploiting classes
The surplus fulfills the biological necessities of the exploiting class.
And it serves a political purpose - it can be used to build palaces, temples (skyscrapers!) and also invested in war and conquest, to maintain cultural hegemony
I agree with that.
Why do Marx and Engels focus on economic classes as the movers of history ? The change agents of society ? Why are revolutions made by economic classes, specifically oppressed and exploited classes ?
Because the economy , the material productive realm of society is where material necessities are met . Things must get done or people will die. Material necessary connections are where Marx and Engels locate the subject of scientific study . Other realms in society, in the super-structure, "necessity" is as in logic or math. Just words; imagined or virtual necessity.
Notice history is especially CHANGE in society.
Notice ultimately we are talking about extremely rare events . Revolutions are rare. True fundamental changes in history are rare. Most of the time of "history" is spent in convention , not invention. Conventional social organization, not invention. Inventions of modes of production is rare.
Because if it's not, we are fucked.
Why not ?
Cause necessity is the mother of invention.