Ethanol gas, Seafoam additive and storage or starting issues.

[Coyote machine]

Lots of times it's about the seals and O-rings and jets/needles and fuel lines getting damaged by the presence of E-10, or its frequent phase separation characteristics, especially in older mowers line trimmers and other gas powered or gas-mix powered equipment. With EPA restrictions on what can go into the air, carbs are smaller with tighter tolerances and less ability to 'fix' problems caused by water contamination- thus things like rust can make getting a smooth idle or run condition nearly impossible.

Sealed containers for gasoline are now the norm, and this can and does help mitigate moisture contamination of gas that sits for long periods of time, especially E-10.