imagine this: an 7th level divination wizard has just finished an long rest and is asked to cast locate creature to find out where all the kindnapped townsfolk have been abducted due to plot. If he cast the spell right away, he would be left with no 4th level spell slots and all other spell slots remaining. Alternatively they could first cast mage armor on themselves, then cast see invisibility, then cast tongues on themselves and lastly cast locate creature, and they would also be left with the exact same spell slots remaining, but now they have a bunch of buffs active on themselves just in case they come across a weird language.

That’s one of the advantages of the School of Divination. It’s a very fun sub class to play!

The tradeoff is that quite a few of their spell choices and prepared spells have to go to that process. 

Do not forget Mind Spike.  Yeah, concenctration with low damage, but to get that 1st level spell slot back it is well worth it.

Or a second or third level slot if you upcast it.

well i used see invisibillity and tounges as examples becuase they do not need concentration and can be cast in a manner that is useful to you just about anywhere, thus the abillity to free up and use spell slots more effectively in the scenario i just listed.

Also if ya gonna use mind spike you might as well use it for its indended purpose: acting as a tracking device to follow the poor fools who try to escape the wrath of your party, rather than just as a way to deal a little bit of damage

It's also useful for battlefields with significant obscurement levels, too.