While visiting Monaco in a backpack and casual clothes is not illegal, it isn't advised either. That's probably the reason why you're getting stares and looks from the restaurants you're visiting...

And while walking towards a huge shopping mall, Monaco spots you while carrying some bags, and decides to make a comment out loud.

Ugh, these poor fucking tourists shouldn't even be allowed here! Told the tourism board we needed a 1000€ entrance fee. Hey buddy, turn around! You can't afford buying things here!