I may be the only one to say this, but I never lunge before I ride, and I own a very, very hot horse (and, in contrast, a lazy one).
I just don't see the point in paying 10-16 dollars for a bag of their feed and then watching them blow away all of that valuable energy.
My horses are taught that when I get on, they are allowed to be fresh (quick to the aids) but that's it. They always are bent and warmed up for 5-10 minutes, and in that time they've always calm down and gotten ready to work--without making their muscles tired so they can't use them correctly when I ride.
But, that's just me. :P
In the process of "teaching" a horse that when you get on they can be fresh but "thats it", it is sometimes best in the early stages to lunge the silliness out. An older horse, agreed, should no better (or a "trained" horse, I should say). But a young horse or one that isnt being worked daily will have extra energy. It's like a child, cooped up inside and then let out into the yard, but told to sit at the picnic table and do their homework. Sometimes they need a little time to "run it off" before they can settle their minds.
Some horses don't need to be lunged, some do better with it.
*But as far as the comment about "lunging" away the money for the feed... a horse gets feed for nutritional reasons as well, not just energy. Many feeds (like a 10/10 sweet feed) will give the horse the nutrition it needs to have energy to work, but not necessarily HOT energy. Lunging a horse to remove excess energy that could cause resistence or unwanted behavior isn't really the same as lunging away all of their energy.
In most cases, lunging before a ride isnt done very long, and isnt long enough to get a horse tired out (unless they are of course having a training session on the lunge line). It is more or less to get them mentally focused not physically tired.