I agree because...
...my briefcase is a working bag and so is my back-pack. Hobos and some natural leathers look better and better with age. I don't think bags are good investments or great bags if one can't actually use them.
however
I disagree because...
...structured, precious, and formal bags shouldn't be thrown around or be stacked when stored. Plus old or pre-loved does not necessarily mean less carefree. My grandmother's and mother's bags looked good when I inherited them because they'd been cared for, I would feel disrespectful if I just overstuffed, grabbed with greasy hands, left pens inside and threw those same bags around.
I don't care how Jane Birkin treats her bags, H may just give her a new one every time her old ones falls apart. Birkins do look better loved and used IMO anyway as they were designed to be casual all-day bags but then if someone has worked for years and saved every penny for their beloved Birkin and hates to put it on the floor or carry in the rain I admire that too. In fact I don't care what anyone does to their own bags so long as it makes them happy.