What are the parallel ridges on grill pans for?

They take some of the dripping fat away from the cooking food.

Yes. They channel the grease.

Really? But since the meat or veggies, or whatever, are soft, most of them will lie on top of the non-ridge part of the pan (the “valleys”, so to speak), so your food is still cooking in grease anyway, no?
Unless, somehow the pan is constructed such that the grease is drained away to the sides. Is that how it works?

The ridges do help keep the meat from sitting on the flat griddle and (on a George Forman) allow some of the fats to drain away and into the drip tray. Think of it as your outside BBQ grill that allows the fats to fall down into the fire. Would you put veggies on your outdoor grill? Not usually. That’s why your kids bought you the Blackstone flat top grill for your special birthday. :-)
The GF grill also is weighted to further force out some of the fats.
If you want to experiment with a GF go to your neighborhood GoodWill store. There are 5 of them on the shelf right now in perfect shape that you can pick up for $5. They are right next to the bread makers and across the aisle from exercise equipment. The world is full of people with good intientions.

It’s not just fats it’s liquid. If you put a lot of veggies in pan the veggies often sweat (some more than others) and the vegetable can become more steamed or boiled in texture than grilled or roasted. When you sauté veggies in a typical pan, and you want them to stay crisp, it’s best not to crowd the pan, because if there is empty space in the pan the steam can cook off quickly rather than collecting. Most of the indoor grills are slightly sloped, so the drippings can run off. A grill pan on the stove still helps keep the juices away from the food, but if the pan is crowded you can still get a steaming effect.

The grill lines do provide a different taste without seeming/burning the entire piece of food, but really nothing is like being on a real fire.

If you look close at the GF grill, it is tilted just a little so the fat runs down the channels, flows out to the sides where there is another channel that directs the grease to the little grease tray. I love cooking my potatoes on the GF grill. The potato stays firm until it is almost done before it gets soft enough to begin to go limp. The ridges press against the potato just enough to leave a thin crust which tastes excellent to my taste buds. A little Cajun seasoning sprinkled over them also enhances the flavor. I have learned by trial & error when to start cooking my potatoes & at exactly what point to add the meat so I have a delicious meal come off at the same time!!!

It also helps to make sticking less of a problem.

All great answers! Thanks, jellies!

@LuckyGuy I’m regularly checking local thrift stores and George foreman grills seem to be everywhere. I’m not sure why they fell out of favor they make great chicken.

The grills are an interesting parallel to the weapons debate. Once you have enough of them out there- – - how many grills do you suppose were manufactured to render them ubiquitous and CHEAP?