I don’t know about the others, but for Apple there’s little evidence that they are trying to use content to lock you in. Music bought on iTunes is now DRM free – you can take all your iTunes music to Android no problem. Not only that, it was Apple that applied pressure to the music labels to bring about the end of DRM.

What of movies and TV? It seems exceedingly likely that these have DRM because the studios want it, not because Apple does. Unfortunately, the studios have the leverage in this case because they managed to make DVD ripping effectively illegal via the DMCA. Consumer’s don’t have a good non-DRM alternative like they did with CDs.

One could make a similar case for books. Scanning in a paperback is not very practical, so publishers get their DRM there too.