Actually I would say that Ryanair is the opposite model. They want to
discourage people from checking in baggage, hence the fees. Staffing check-in desks and paying for baggage handling is a cost to the airline and increases turn around times as bags have to me moved on and off the aircraft. The difference is that Ryanair passengers are not, generally, making connecting flights at their destination at least not with Ryanair. They are flying straight to their destination, removing the advantages of checked baggage that exist for Southwest.
As for the fees, that is a feature not a bug. It means that people who want to fly as cheaply as possible can (no frills) and those who want the extras such as checked baggage pay. With a no fee structure, essentially the people who don't check baggage, check in online instead of at a desk, don't care where they sit (and speed up boarding times) etc are subsidising those that use those extras.