I did a sub contract event where I was brought in as a "SOUND TECH" and not a DJ. The bride and groom really only booked a "Sound Tech" because they did not want to handle the logistics of the ceremony and reception sound system. They could have rented all of the gear, but putting someone in charge of getting the gear at a guitar center for example, and bringing it to the venue, setting it all up and tearing it all down is problematic and can be a challenge for the couple.
I provided microphone sound during the ceremony along with playing their ceremony songs. After that, I was literally letting a playlist on spotify play for cocktail hour, and then they had a dancing playlist set up. I pressed play on the dancing playlist when it was time to, and I walked away. Yes, people did dance and have a lot of fun. I even got a tip on that event too.
I will add that I did not do any MCing/make any announcements, and there was no planning on my part besides asking for my ceremony set up spot and discussing if I needed tables provided or not (I did bring my own tables and made it even easier on them). They emailed me their Spotify playlist links a few days before their wedding.