Comment Re:It's all about entropy (Score 1) 467
If all you ever want to compress is files which contain the same byte repeated many times, then yes, that's how you would compress them.
But most compression formats are tuned to produce good results for the sorts of files which people are more likely to need to compress; so even when run-length encoding is used, it will typically have a low limit -- say, 255 -- on the run length.