A lot of companies are switching from old-school fluorescents (which aren't quite as efficient) to LEDs as the fixtures wear out. And yes, they do wear out, along with things like ballasts. There are a LOT of the old T12 fluorescents out there still, not to mention the newer (but still somewhat outdated) T8.
They also make LED tubes now - a line of LEDs in a package the same size as the old fluorescent tubes. They cost a lot, but over the long run, they're cheaper to run. Once you include lowering air conditioning costs and less manpower spent replacing tubes, they're often worth the money. All you need to do is bypass the ballast (which also saves money in the long run - those things wear out too).
A lot of factory floors used mercury vapor lights, and those are going away as they get old, replaced with clusters of LEDs.