Originally Posted by
FrequentFlyer9000
...whereas business class full-fare is common especially among business travelers.
Not really. Corporate contracts and such mean many are paying discounts there, too.
But to the OP's question, the market for F is shrinking rapidly. There are very few routes/markets in which passengers will actually pay - be it full fare or contracted discounts - for first class. It is disappearing in general, though it does remain in a few niche areas.