The animals barely remember life before the Rebellion because

This is because the animals' lives are comparatively short to humans. As the original animals of the rebellion die off, the conflict becomes more removed for the new animals,

"Years passed. The seasons came and went, the short animal lives fled by. A time came when there was no one who remembered the old days before the Rebellion, except Clover, Benjamin, Moses the raven, and a number of the pigs.

Muriel was dead; Bluebell, Jessie, and Pincher were dead. Jones too was dead-he had died in an inebriates' home in another part of the country. Snowball was forgotten. Boxer was forgotten, except by the few who had known him."