Storing the domain in the DB may be reasonable if it's done once, but WP does it multiple times: WP_SITEURL ("the address where your WordPress core files reside"), WP_HOME ("the address you want people to type in their browser to reach your WordPress blog") and of course GUIDs for every post have the domain hardcoded into their values (that can mess up links in a weird way, where you're on your local environment, click a link, and now you're silently on prod).
I could definitely be missing something, but I can't for the life of me figure out why this is a good idea.