Nothing to argue about arbitrary disdain for backpacks ¯\_(ツ)_/¯, but I don't remember one backpack that I saw and thought "wow that backpack is ostentatious, that guy is a showoff". Not once.

They also mentioned theft deterrence as secondary goals, so my recommendation stands for everyone else who doesn't have random hatred towards backpacks. :)

It might not be ostentatious looks that are the problem. Dell used to be big on up selling rucksacks and briefcases. Their bags were never good looking but they did advertise the contents of your bag as likely to contain a Dell laptop - 'please steal me now'.

As for bags as status symbol, men don't go into that but women have these things called handbags. No man in history has been interested in a woman due to her taste in handbags, which is fine since the signalling is only to other women. Compare with cars where a Porsche is only going to be noted down to model number by men, with women not caring about the specification, to them it is just a Porsche with colour being the only noteworthy aspect.

Naturally this does not apply to all men or women, however, there are patterns. Showing off is also about poor utility. A rucksack designed to carry a laptop is far too functional to be high status. However, if you make a handbag and design it so it can barely carry so much as a toothpick, then that is high status, much like how a Porsche car is high status because it is essentially not practical.

A laptop bag designed for the task, much like a Dell laptop bag of old, might stand out as advertising its contents but it is far too well designed for the task in hand to be desirable. Hence the owner won't be a showoff.