I know quite a few travelers who always travel with a carry-on bag, and I see even more during my trips.
Whether the purpose is to save time at departure or arrival by not having to check-in and wait at the baggage claim, or to fight the fear of losing your stuff, you should know that this is not free; it comes at a cost, and that cost is my time (and the time of everyone else who did check a bag).
By bringing all your stuff with you, you slow down the security checks, slow down boarding procedures, and slow down everyone when leaving the plane.
On today's planes where as many passengers as possible are squeezed, it's obviously impossible for everyone to carry their bag.
As a result, those who do are saving time at the expense of those who don't.
Airlines should charge for carry-ons, not for checked-in luggage.