robots.txt was originally created to include such bots. That they think they don't need to respect it goes against the original intent.

I want my software to obey me, not someone else. If the software is discovering resources on its own, then obeying robots.txt is fair. But if the software is polling a resource I explicitly told it to, I would not expect it to make additional requests to fetch unrelated files such as a robots.txt

I can almost see both sides here... But ultimately when you are using someone else's resources, then not respecting their wishes (within reason) just makes you an asshole.