I am wondering why cereals such as oats and wheat need to be planted
every year, at expense (labour and machinery). The grass on my lawn
seems to keep growing from year to year, even after cutting.

Does wheat die after ripening and forming seed? Even if the plants
lasted two years before ploughing and e.g. growing beans then that
would save a lot of fuel. Is this what zero tillage is about? Is
ploughing needed to cut down on weeds?

Can you buy perennial cereals, or are there people working on breeding
(or genetically engineering) them?

Dave.