"Why does anyone need a separate dac?"
Someone may wish to play sources other than files (e.g. discs). I don't listen to discs so it's not a big deal to me. Here's a review (including the price) - https://audiophilestyle.com/ca/reviews/review-lumin-x2-flagship-network-player-with-discrete-dac-r1420/
I currently use a Lumin U2 (with an EMM Labs DAC 2x) and had a Lumin U1 before that (I use an all in one Lumin M1 is a spare 2-channel system in a small bedroom). I might eventually consider the X2 down the road.

