Why?

This is a shot of the bookcases in a corner of one of our rooms. There is another bookcase in the same room. In other rooms there are more bookcases -with more books in them, obviously!
Now the question is 'Why?' I've read a lot of them; most of them could be downloaded onto my kindle; some, like the Jane Austen, top right are on my kindle. How many of them would I re-read anyway?
Blippers... I need your help! Am I keeping these for sentimental reasons? Do I think that a house without books is unfurnished? If I re-homed the ones I could easily find on-line would I feel okay without them?
Advice please!