Well, the theory goes a little something like this: when a prospective buyer walks through your home, you want them to be able to visualize themselves there. By removing your photos or other personal items, it will be easier for people to imagine the property as potentially theirs.
At least that’s the theory.
For my part, I think it’s a logical approach – and those items will need to get packed away at some point, so better sooner than later. If it plays a small part in helping someone imagine themselves as the new owner of your home, it’s worth the effort to pack those items up.