I think they're relatively "new" to landscaping. Today, looking around at most landscapes, you're bound to come across some form of ornamental grasses. This time of the year, they seem to be everywhere. As part of my communities' landscape design they're growing at the end of my back yard and they are absolutely beautiful.
Ornamental grasses offer graceful habits of movement. If you watch a group of ornamental grasses on a windy day, they seem to be swaying with the autumn breeze.
I planted a couple of small ornamental grasses in my rock garden back in June. Today, one has pink plumes and the other, wheat color plumes.
I can imagine in the next few years these plants will look pretty much like the ones at the end of my backyard. How wonderful that will be!