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Albums are generally mixed primarily for speakers, not headphones. With speakers your right ear will always hear some sound from the left channels (and vice versa) - this is crosstalk. You can get some (intentional) headphone crosstalk with a feature called crossfeed. There are crossfeed plug-ins and phone apps.
Grew up in the digital music age so I never really knew the difference until I started playing music and I gotta tell you, I’m not sure if mono is better (music enjoyment is 100% subjective) but there is this genuine quality of mono that brings music to life IMO. Good post OP