Totally agree with the dislike of the castering-wheel suitcases. For a start, they are fragile and it doesn't take much of a drop to ruin one or more wheels thereby turning it into a boat anchor. The ones with two fixed more-protected non-castering wheels are better, but you still need a smooth surface. The glitterati might frequent only high class cities, but even there sometimes cobblestone surfaces are desirable and maintained. In the parts of the world I live in there might not even be a footpath/sidewalk, much less one with a smooth surface, so a backpack is better. I can live indefinitely out of a 25 liter pack.
Don't grow old. Well..do, but bear in mind your balance with a loaded back and risks of back injury aren't zero. Not that pullalong or pullbeside cases don't have other risks.