For those who have been off-roading, the following is probably TLDR; feel free to skip to the next post about TPMS systems.
Maximizing traction when off-roading is the name of the game. And lowering tire pressure is the easiest of things to improve traction. Dropping the tire pressure allows the tire to "flatten" out, opening the tread pattern (better for dirt and mud) as well as increasing the cross-section contact patch.
While going from 30 psi to 20 psi doesn't look like much tire deformation, it can nearly double a tire's traction.
Too low of a tire pressure, however, runs the risk of unseating the tire's bead, the metal wire built into the tire that creates an air-tight seal against the rim ). If this happens, it isn't the end of the world as it's an easy fix even on the trail; jack up the tire, use a ratchet strap to push the bead against the rim and use an air tank or onboard compressor to fill the tire. But it's a pain and definitely brings the entire off-roading convoy to a halt for a good half-hour. On stock rims, I tend to "air down" to 15 psi without much risk of this hassle.
After-market "bead lock" wheels allow the tire pressure to go even lower by providing an inner seat in addition to the outer one; effectively clamping the outer bead between the rim (green) and another plate (red) bolted together (yellow). This is a single beadlock configuration as the inner bead does not have a similar attachment; tire pressures can be lowered to 10 psi or lower
Little Bo is soon getting Hutchinson Rock Monsters with Toyo Open Country Mud Terrain 33s. That is to say double beadlock rims, whereby the beads are held in place against the rim using a hefty 3/4" piece of rubber sandwiched in between two piece rims. (pictures to follow)