I attempt to reply to each person who leaves a comment. There are a few I felt like just deleting. I believe in full disclosure so have to use my business sense to answer a few. In business they call it reputation management.
Why? because each reply brings the hub back to the feed. I believe like most I write for exposure. Since I search the hub pages feed daily for information to share with business associates and anyone who might be interested, I like seeing my work on the feed.
In my time on hub pages I have seen people with literally hundreds of comments to a single hub. In each case there was a reply. In time comments stop coming. My advice would be create a document in a word processor to add if you don't have time to reply to each. Copy and paste, soon comments will stop. No one likes seeing the same comment time after time. Until they do stop you will still be put on the feed.