What is the purpose of this on my tiller?

[NWHmoob]

I gave up on searching for this so I'm going to ask. What is the purpose of these wheels on the rear of my tiller? Nothing is wrong with it but I'm just curious. I have notice that with it off I'm able to till deeper but what is the reason for it's purpose in life.

 

[Redbusdriver]

Gauge wheels. The clue was in your comment. More common on a plow than a tiller.

 

[Ramos]

Those are gauge wheels for depth control. Set your depth with the wheels then give your three point 'full down'. Allows the tiller to float over highs and lows while tilling at a consistent depth.