I can understand the use in agriculture, but I've never understood why anyone would use the stuff on their own lawn. Who cares if there are some weeds growing, when you can cut them down with lawnmower anyway?

Heck, my relatives in the countryside don't even have lawn, they just let the dandelions and other natural plants grow, and only use lawnmower in areas where they need to walk. Much better for the environment, and even looks pretty nice. Of course areas where they grow food or fancier flowers require some digging to keep weeds away.

Cutting dandelions with a lawnmower just sends the seeds everywhere making the problem worse.

Some neighbors spray poison ivy --- I just cover it with stones/bricks when I see it.