I collect flac wherever i can on my Computer and sync it to my phone with transcode to lossy. I agree tho, a good lossy encode cannot be distinguished from their lossless version. Even less when you dont have the immediate comparison.
Three reasons:
- collectors appeal -> music on the internet comes and goes. Chances are that your file that you downloaded randomly becomes the only one available. having it in best available quality is the icing on the cake.
- generational loss -> the ability to transfer your music to any future media you like without/with minimal loss. Also if you remix/cut/edit stuff it keeps quality high
- killer samples -> given more agressive music, codecs might fail. There are some examples on hydrogenaudio.