As for sr2 there is the mod: Cutscene Patch.
Make sure to download the No Letterbox Edition.
Just be sure to understand that some scenes will look odd since the cutscenes were not meant to be seen without them. Eg: Floating characters, legs clipping into floor objects, Etc.
And as for why it's a thing, it's to mimic movies and make them appear more cinematic.
And it's probably possible for sr3.
Edit: Just realized I responded to a year old post. I'm braindead.