Why do people like contravariant functors more than covariant ones?

In most category theory texts and in applications I tend to observe that contravariance is given more page presence than covariant ones. What are the reasons behind this(if this is a valid observation)? One reason I can think of is that in geometry people encounter contravariant functors more often than covariant ones. Another reason is probably that letting your functors be contravariant let's you in turn have the embedding of the category into the functor category as covariant and hence this is a nice way of looking at objects of a category as functors.