There are many reasons;
1. Easy to rip a Redbook CD to FLAC but not as easy to rip a SACD to as DSF format.
2. Many of the streaming services only have newer remastered versions that many times are brick walled or not as well mastered as what you may own in the CD format such as a Mobile Fidelity or DCC mastering.
3. If a friend comes over to listen to music they may be interested in hearing how their CD sounds on your system.
4. With a good CD transport, DAC and great mastering you can compare digital to analogue and hear how digital sounds just as good and maybe in certain aspects better than analogue.
5. Fun factor in going to your shelves looking over a collection of great music, picking one to listen, sliding it into the drawer, pushing play and sitting back to listen as you read the pamphlet and back cover along with enjoying the art work. I admit certainly not as nice as an album cover but if you don't have that recording in vinyl it gives you a miniature version of the experience.