I know its because of the TV rights - Sky, Sport1 etc and I understand in a way but, as a fan wanting to be at the match it does create problems.
On a Friday night it must be awkward at best for an away fan having to cross Germany to get to a 17:00 kick off. As for Mondays . . well forget it. At least you can watch it on free tele I suppose but it's not the same as being there.
The match can be on any one of four days spread out over a weekend and you don't know which until a few weeks beforehand. This is a bit of a nightmare for away fans but also home supporters travelling to a match from far afield.
Forget "book early to avoid disappointment", it's more like book early and take pot luck!