Even if you have enough bodies when you leave your turn, they might die to removal and such
Against control it counters draw and removal, against aggro it stops creatures, and against combo, it disrupts key combo pieces
Rather than staying as a selection of generically useful picks, these 40 cards will vary from set to set, being more closely tailored to each sets theming and design
While on the surface it looks like she has infinite possibilites -- you can tutor for ANYTHING -- in practice, all Prime Speaker decks are going to end up the same, tutoring for the best creature target and following the same lines of play so you can combo off the same way each game
On turn 6, you wont have any more counters to remove and will have to exile Parallax Tide and your opponent will get all their lands back