A lot of more experienced riders are going to a 46 tooth for their largest front chainring. They can still pedal at 25 mph at a comfortable cadence and if they need a burst of speed they just pedal faster. A second chainring with 36 teeth (or third with 26 teeth) can be used for steep hills or hills when you're loaded, towing a trailer or a trail-a-bike.

If a downhill is faster than 25 mph you're better off from an energy management view to stop pedaling, tuck-in, and let gravity do its thing. The only other use for a big chainring is if you have a really strong tailwind but once again, you might want to save your energy for the trip back.

None of this applies to racing where tearing around at 25 mph is the norm and big chainrings do have their place.