Backpacks were not just for students but also for young mothers, busy businesswomen and those who want both hands free. LV still makes backpacks these days.
For the Cabas, IMO, it's obviously trendy. The bag was on runway. So, it became hot bag. Let look at the original Cabas. With the size that big in leather, it must be real heavy. How can it be carried on the shoulder comfortably? Is it too big to carry as hand held? Imagine walking around with a bag almost hit the floor? Isn't that more bizarre?
The bigger the bag, the more things people throw in. How can they conveniently find thing in a bag that deep with such a small opening?
Impractical, inconvenience and too much strain put on the shoulder, eventually, the style will die out. Let wait and see.