Why did the peasants not enter the feudal ladder?

This is due to the fact that they were not feudal lords. The peasants did not own the land, they worked on it. We can say that they belonged to their feudal lords. At that time, only feudal lords could enter such a feudal ladder. In the feudal staircase itself, that is, at its top, there was a king, then there were counts, margraves, then dukes, then barons and knights. Outside the feudal ladder, there were, in addition to the peasants, the townspeople.