There are almost no reasons why a person has to bring a bag. Maybe someone like an insulin dependent diabetic, then again they are likely to bring just enough supplies for the day and those will be tossed if they use them. If not they could end up left on site so they won't be forgotten at home. A girl needing tampons, again used and trashed.heck they can even be in a pocket. Last I checked no one was patting down employees pants etc to make sure they went hiding iPads in those giant pockets.
Again, I've listed several items that people may have to carry that aren't disposable.
You seem to be only looking at this from your own point of view, and not seeing that other people have different needs than you, despite several people showing you otherwise.
I've listed about 6 or 7 just from my own experience. There's a guy where I work that has severe vision problems. He can see (barely), but needs to carry a white stick for crossing roads coming in and out of work. Where should he keep that?
There's also people who have to wear hearing aids at home and at work, but not necessarily while travelling. They bring them to work in a bag, because that's the most sensible way of transporting them, and they often can't afford two sets.
There's about 30 or 40 people in my building who cycle to work. They have helmets and other equipment that often needs carrying *in a bag*.
There's also people I work with who have medical issues that are really quite personal. They'd rather keep things related to that in a bag, hidden away, so that they don't have to be judged by people less tolerant than some. A really good place to keep those things is in a bag.
There's a reason lots of people use bags - they're really handy, they give you privacy, they save you money in the long run (my satchel cost £3 in a sale, I've had it for 3 years). Stop telling people what they do and do not need to do based on your limited experiences of your own life. It's asinine, borderline offence to those who it dismisses, and wrong on a number of levels. People are calling you out on it. Listen to them.