The main reason why most music downloads are still only in MP3 quality is because it's the most compatible format, which can be played in computers (of course), on all portable players, and most newer generation car radios and DVD players. The hardware that supports FLAC is still quite rare, especially with portable players.
The initial reason for MP3 - limited internet bandwith, limited storage capacity - is hardly relevant anymore.
So I think that as soon as the major electronics companies support the same lossless compression codec, the market for lossless downloads will explode.
Buying a rare OOP CD for $40 on Ebay or paying $10 for a lossless download of the same CD, my decision is easily made.