It's so that the maximum number of games is played on the last game-day preceding the play-offs. That's understandable, and the NHL does this, too. (All 30 NHL teams were in action on the final day of this year's regular season, but it was a Saturday.) It's unfortunate that at the Worlds, this last preliminary groups game-day was a weekday.
If it were up to me, I'd prolong the Worlds so that it lasts 3 weeks plus the foregoing weekend (as it does now). The schedule is too packed right now. Slovakia played its first 4 games in 5 days – that's insane. This isn't the AHL; it should be the climax of the hockey season.
So, I would use the first weekend + 2 full weeks for the group round-robins. The last Sunday would be that big final game-day with 6 games in total played.
Then, the final week would be for the play-offs only. Only the 8 best teams would be in action in the final week. Monday would be a rest day. Tuesday and Wednesday would be for the 4 quaterfinal games, Thursday and/or Friday could be for the 2 semifinal games, Saturday for the Bronze Medal Game, and Sunday for the Gold Medal Game. Just take it easy. This is how the football World Cup does it to build up tention in the play-offs stage, and it's great. There's no use hurrying. I hate it that tomorrow, there are 4 quarterfinal games at the Worlds, but you can't even properly watch them because two pairs of games partially overlap.