Reply to Pre-Mixed Tracks?

So I came across a dj that plays all the parties at my uni the other day on Soundcloud, and I was kind of surprised to find that in their mixes, about half of the tracks they played were premade mixes. Just two tracks that they'd mixed together and then they played that mix.
Not judging per se, but I personally feel that that's a bit of a cop out, because they're essentially doing half of the mixing necessary. I listened to the mixes and they weren't even intricate mashups that couldn't be done live, they were just moderate length blends with effects.

Has anyone on here seen anything like this/do this/what are your thoughts?
Peace