I think it's important to take a moment to consider the design impact of tutors. You may look at a card like Demonic Tutor and kind of wonder what it's really achieving design wise, and perhaps the biggest benefit is to give decks that require certain pieces some redundancy. I always like when I play a cube deck with a unique gameplan, and something like Demonic Tutor can really tie it together. I also consider them to be rather decision dense cards. Sometimes you have to tutor for a land. Sometimes you have to spend mana on it in an earlier turn because you need to tap out on following turns, and have to try and guess where the game will progress. It's pretty rare that a given tutor will always grab the same card in one of my decks, and I find that pretty enjoyable.
Trinket Mage packages are also super fun, and cube actually provides an appropriate power level for them depending on your configuration. It's a card that goes in and out, based on whether I have Dimir Tezzeret in or not.
