I noticed some tackle box/tray companies sell 3700s in a deep version. What do people typically store in these deeper versions? Just a bigger quantity of stuff you store in usual 3700s? Or can you fit buzzbaits/spinnerbaits in them? 

Yes. Spinnerbait, Buzzbaits, Magnum spoons, big swimbaits, 10xd/8xd sized cranks, etc.

The real purpose is when you get a number 1 wacky worm hook gets stuck in the corner you can jamb it in the end of your finger. 

Whatever fits.. 

Scissors, bobbers, jars of powerbait, bandaids, a metal stringer, sun screen, backup sunglasses, bug spray, a matchbox car, a copy of my boat registration and the years fishing regs, three rotten rubber bands, the wrapper from a pack of hand warmers,  small tube of dielectric grease, the remains of a toothpick used for pinning a float, crappy rusted pliers...

 

It's like a junk drawer for the boat.  

More crankbaits than I will ever need in a day.