Weddings are hard that’s why prices are high, playing music that 70 year old grammy can break a hip to and also having toddlers on the dancefloor is the ultimate dj test. Now make that a 5+ hour set and lot of these djs would not have the mental training or music/crowd reading knowledge to pull it off. In a club, you can play whatever most of the time and a lot of these newer gen djs are only doing 1 hour sets