Should I write for an audience, or to please myself?

Dear Literary Ladies,
These days, publishers want to know how authors plan to find the audience for their book well before the final draft is submitted. It’s all about marketing and platform, which can be awfully daunting, as well as distracting. Do you think writers should focus on the audience or market as a work is being developed, or does that ultimately make for a less desirable outcome?

Those critics or well-wishers who think that I could have written better than I have are flattering me. Always I have written at the top of my bent at that particular time. It may be that this or that, written five years later or one year earlier, or under different circumstances, might have been better for it. But one writes as the opportunity and the material and the inclination shape themselves. This is certain: I never have written a line except to please myself. I never have written with an eye to what is called the public or the market or the trend or the editor or the reviewer. Good or bad, popular or unpopular, lasting or ephemeral, the words I have put down on paper were the best words I could summon at the time to express the thing I wanted more than anything else to say.

—Edna Ferber, A Peculiar Treasure, 1939