Perhaps it is easy to sing a medley, since most songs have common words. It's just a matter of tune and rhythm. and pitch. Perhaps not.
I went for the Acapella Championships just now. College and Open category. Honestly, as I heard the first two groups, I contemplated the loss of twenty bucks - the cost of my ticket. Then the third group came, and it made every cent worth.
Probably waaaaaaaaaay back many eons ago, acapella championships were, well, acapella championships. Pure blissful singing and nay a gesture of artistic creativity. Speed up to the current era, and competitors nowadays have it harder. Wider repertoire of songs to choose from, fashion themes to consider, steps to be practiced and roles to remember. You can't just stand and sing. You gotta dress nice, move nice, skip a little here sway a little there blah blah blah.
Of course, if school bands engage the audience attention with their acrobatic movements, and school choirs dabble a little in dancing or comedic storyline, then it would only be a matter of time before acapella groups follow suit.
Now, it just makes me wonder, if so many music groups are doing dances and weird stuff, what about dance and weird stuff groups? What, they gotta sing now?