Buying Hebrew servants?

Exodus 21:2 says, “If thou buy an Hebrew servant, six years he shall serve: and in the seventh he shall go out free for nothing.

21:3 If he came in by himself, he shall go out by himself: if he were married, then his wife shall go out with him.

21:4 If his master have given him a wife, and she have born him sons or daughters; the wife and her children shall be her master's, and he shall go out by himself.

21:5 And if the servant shall plainly say, I love my master, my wife, and my children; I will not go out free:

21:6 Then his master shall bring him unto the judges; he shall also bring him to the door, or unto the door post; and his master shall bore his ear through with an awl; and he shall serve him for ever.”  I thought they had just survived the exodus from Egypt, but why would they be buying and selling each other so readily?  It reads that if you are a girl sold into servitude it is forever.  That would be slavery.  Why would god tolerate this?  Women have no value in this book once again.