Well, you've just revealed which kind of “content” you watch (by revealing which kind you don't). A lot of well known films were shot on full frame, and never had any other variant.

Frankly, seeing them in theatres “as intended” would require inventing a time machine, or not missing some special film screening event, as they were made quite some time ago.

Also, back then, when they still had to make film prints for distribution, and had to deal with wide screen theatres and regular screen theatres (you couldn't just ignore the other half, and lose a potentially significant share of income), both filming and editing took that into account. Shots in one aspect ratio were usually composed to look god when cut to the other, and professional cameramen (working with both types) constantly kept that in mind anyway. Same for possible TV screening versions later.

Now compare that to the modern nameless editors working for giant corporations which pretend that it's an impossible task that has never been done, and either crop automatically, or let the “smart computer” toss a coin to shift responsibility.

Edit: By “theatres” I've meant types of film projectors installed in their halls. Some had multiple, switchable lenses, etc., some had only one. Keep in mind that to show a multi-reel movie without pauses you need at least two projectors (or a special feeding system for spliced together film if the number of screenings is worth the work), and a third one is often added for redundancy and required maintenance work, so there's a lot of investment to make already.