From Sony Corp. of America v. Universal City Studios, Inc., 464 U.S. 417 (1984).
The sale of copying equipment, like the sale of other articles of commerce, does not constitute contributory infringement if the product is widely used for legitimate, unobjectionable purposes, or, indeed, is merely capable of substantial noninfringing uses.
there is a significant likelihood that substantial numbers of copyright holders who license their works for broadcast on free television would not object to having their broadcast time-shifted by private viewers (i.e., recorded at a time when the VTR owner cannot view the broadcast so that it can be watched at a later time); and (2) that there is no likelihood that time-shifting would cause nonminimal harm to the potential market for, or the value of, respondents' copyrighted works. The VTR's are therefore capable of substantial noninfringing uses. Private, noncommercial time-shifting in the home satisfies this standard of noninfringing uses both because respondents have no right to prevent other copyright holders from authorizing such time-shifting for their programs and because the District Court's findings reveal that even the unauthorized home time-shifting of respondents' programs is legitimate fair use.
we must conclude that this record amply supports the District Court's conclusion that home time-shifting is fair use.
This is distinguishable from downloading movies because in the case of videotape or PVR recording, the copyright owner authorized the broadcast, and private, non-commercial time-shifting at home has been held to be fair use.
When downloading a movie, the copyright owner did not authorize the communication, and copying movies by downloading them from an unauthorized source is not generally considered fair use.
One policy reason why this difference might make sense is that when time-shifting, you are usually paying for the channels, and they are in turn paying the copyright owner for the permission to transmit their work. However, this is only a guess, and not really relevant to your legal question.