As bags are useful, I can understand why people would want to own several. For business, travel, day, evening, woman or man, each situation demands its own bag. There is the duffle for clothes and the odd short trip, briefcase and portfolio for papers and the day's newspaper, clutch for the evening's necessities, tote for shopping, and luggage for getting away; not to mention the cases for laptops, and bags for shoe, makeup, toiletries and even lunch. Hard-sided or soft-sided, in different colors and materials, hand-carried, messenger-style or over-the-shoulder, there really is no end, nor does there need to be, to bags.
A fantastic bag makes a fantastic accessory - a window into the wearer's personality and mood of the day. Maybe an unstructured bag for a change of line, or a hard-sided brief for an air of seriousness? I like my bags to have simple lines and a sense of purpose as they are entrusted with carrying my possessions. Whatever the case, you carry the bag, do not let it carry you.
How you use your bag is up to you. I will only say that it is not nice to sit on other people's bags, but then it is not nice to leave your bag on someone else's seat either. I like to change which ones I use to suit the mood of the day. I find bags useful as I do not carry things in my pockets but still manage to carry many things with me. To borrow a saying, it is all in the bag.