Because they are being told or have read somewhere that fuel goes bad after a while. So, they follow the instructions of some other halfwit to get rid of all the gas before they store the unit and run it dry (so they think).
You are speaking in past tense about your Lawnboy, which makes me believe this all happened before we had ethanol in gas.
It has been a while since we had the Lawnboy. It's also hard to remember exactly how the timeline runs as far as when, in our ownership experience, that ethanol was introduced to automotive fuels. I imagine the Lawnboy started life without the benefits of alcohol in the gasoline but I'm more than certain that it didn't finish life with that advantage. We were just amazed it lasted as long as it did. We do have a relatively small yard. I can mow and edge in about 50 minutes so it's not like the mower had a tough life all things considered.
You didn't answer my question though. How does running all the fuel out of the mower before storing it for the winter damage anything? I agree, the fuel will go sour over time unless it's treated but I don't see how storing it dry for one season poses any problems?
Again, just wondering?
Ride Safe,
Steve R.