They might be good to allow water to drain out of the pots more easily than being sort of plugged by the ground itself.

Lifting pots above the ground protects them from sending roots down into the ground, which can be a problem in some situations or purposes.

Those half-rotten pieces of wood look nice for hugelculture. If you happen to need to dig deep down in a bed, throw those wood pieces in at least a foot down, and cover with compost and soil. It is said to conserve moisture, and plant root are said to love it.

@HighColdDesert That's a great idea! I'll have to pick out the pressure treated pieces. Thanks!

As said above, lifting pots off the ground allows for drainage, roots not going out of bottom of pot clogging drainage hole, and, to some degree, insect invasion.