Normally, you’d think pointing out that someone tracked dirt through your home, or that a window was covered with a certain bird “souvenir,” would be an insult.
When isn’t that the case?
When a Realtor doing a preview or showing encounters those things, and lets the listing agent know.
That’s especially the case when a home is unoccupied, and the offending condition would otherwise go uncorrected — until the next prospective Buyer came through.
The same courtesy applies — only more so — when a Realtor encounters a home with an unlocked (or open!) front door (not common, but it’s been known to happen, especially with unoccupied homes).
Then, alerting the Listing Agent not only serves to protect an otherwise vulnerable home owner, but takes the agent reporting the problem off the hook for any security-related problems on the premises.