In the months of summer and early autumn, the Nile flooded a lot of these farmers' fields, so helping with the pyramids was the way these men supported their family until crops were workable again. Not only did they get food and minimal wages, but helping with the pyramids counted as brownie points for the gods, and anything they could do to get ahead with Amun-Ra and the gang, they were going to do.
All in all, historians estimate that about 10,000 of these lower class workers helped out--without having to be whipped into it.
While we're talking about Egypt, there was a long time when Egyptian kings were not called pharoahs. Not until the 14th Century BC did that word start going into circulation, and even then it was used to describe the royal palace, the capitol, and the king himself. The derivation of pharoah, Par-o, actually translates to "Great House." It was the Israelites (i.e. "slaves") who gave the title to the king in their scriptures, and around 950 BC "pharoah" became the official title for Egyptian kings.