The purpose is to resell it.
Unfortunately, most TNG watchers doesn't look on it as a piece of art but as entertainment.
Paramount's options are to either crop it or have the Average Joe spread the picture wide and make Picard look as fat as Kirk. People want to fill the screen one way or another. I sold widescreen TVs for too many years, preaching the advantages of window boxing (with the bars on the sides) only to see EVERY SINGLE ONE of my customers, even those ones with 10' screens, either zoom in on the picture or opt for spreading the picture wide and fat. Every single one wanted the picture to fit their new wide screen. It was disheartening but a great wake-up call.
Don't believe me? Take your own poll. Have you ever gone into a bar or restaurant with widescreen TVs and NOT seen a 4:3 picture that is either spread wide or zoomed in and cropped? I haven't.
I'm just telling you that yours (or my) purist Trekkie objections be damned, TNG-R would be in widescreen because that what people want to watch.