A small inheritance/dowry is still an inheritance/dowry. Also the transaction of a woman providing a man with children, in exchange for economic and physical security, is as old as civilization.

Poor young women literally had no alternative to marriage beyond a few ill-paying professions.

Marriage was mostly a contract where the man say he is responsible for the kids born by the woman and the woman say she wont have kids with other men.

No, it was actually true of a very large segment of population at least in the 18th to early 20th centuries in europe / NA : small farmers a.k.a 70-90% of the population

Marriage was a transaction for stability and security for the lower class as well.