Why not? And for what applications? Example: for a media streaming service, where each file is transferred many times, the bandwidth costs dominate, so it is worthwhile to spend a great deal of time on encoding to maximize efficiency. In the case of an archive, where a large amount of information is stored, accessed infrequently, storage space becomes the constraint, once again. In general, 1 marginal second of CPU time is usually cheaper than 10Mib of marginal storage (or whatever the figure works out to be). Finally, why not just write a fast FLAC encoder?