Apart from iTunes, what lawful download store for Hollywood movies were people using during this period?
Not really sure what the point of this question is. In case you haven't seen a calendar recently it's 2015 so the fact UV only came out in 2011 is next to meaningless.
Things change in the home video world from time to time and collectors are always faced with the decision to upgrade or simply maintain what they already have. For those who transition they have two choices to make;
1) Maintain both systems which on the UV side requires next to no work since most internet capable video devices can playback UV movies but does require the person to maintain specific hardware to access their iTunes library.
2) Convert/re-purchase the things you really want in the new system. This can be expensive but is not unusual for a collector.
It's a choice that has been made several times over by most video collectors and I'm sure will be made again at some point in the future, possibly when 4k really takes off and iTunes and/or UV offer 4k upgrades from their previous 1080p only versions.