Makes sense.
I do think you are on to something with the socialization idea. They may have gradually realized that there was safety in numbers. Groups can gather more food, evade predators better, and fight battles with enemies more successfully than individuals. That seems like common sense to most of us but there was likely a learning curve for early man. In a group setting it is generally the elders that mentor the younger members, so older members would have been valued more than in the past. Groups have many tasks that have to be done by someone, so weaker members would have been able to contribute something and would likely have been valued more for that reason.
Makes sense.