In fusing together some notes on models of state and society, I came to another reason of why history is so important, even in the case of theoretical models.
The work of Miliband, Poulantzas and other Marxists from the 1960s and early 70s examined the relationship between the state and capitalist society. Their work was motivated by the desire to explain why capitalism was still, in the 1970s, the dominant economic system, given Marx's predictions of its certain collapse.
Block, Przeworski, and Wallerstein (later 1970s and 1980s) were also motivated by a central question. They aimed to explain how labor was able to make such significant advances in terms of wages, and working conditions, and collective bargaining institutions more generally since the late nineteenth century, all of which were strong indicators of the development of the welfare state model of capitalism.
Both groups of theories trying to explain the exact same period (and arguably, depending on your notion of objectivity, the exact same phenomenon), and the difference in how the question is framed makes all the difference in the outcomes of the theories...