Cut and "come again?" (2)

The Man writes...At the weekend, Albaniana turned to me and said: "It's not your fault, but because those dandelions weren't cut back before they seeded we're going to be overwhelmed by them next year."

Maybe someone could please clarify for me what the words it's not your fault mean in this context?

Taking the hint, I assembled and fired up the new mower. This required fairly close reading of a rather intimidating Operator's Manual. "Warning!" it proclaims. "The engine exhaust from this product contains chemicals known to the State of California to cause cancer..."

Lucky we live in New York!

"Important!" it continues in bold type. "Engine is not equipped with a spark arrester. It is a violation of California Code Section 4442 to operate the engine on any brush-covered or grass-covered land."

Slight drawback for a Lawn Mower would you say?