When I was a kid I got caught sneaking on the subway. I was charged with theft of services. It makes sense to me - what I literally did was evade paying my $1 before stepping on the platform, and I was attempting to ride a train that wasn't full, so my being there or not wouldn't affect the operation of the train or the other riders. But gaining access to something against the wishes of the provider jeopardizes the provider's ability (or incentive, or willingness, whatever) to provide the service. That's why it's called theft.

This is all kind of off-topic to the OP, and doesn't address why people should or should not pay for their software, music, and movies, but I think theft or fraud is an accurate term to use.