Frontier is a sham. Their published "discounted" fares are only for a middle seat, and includes no carry-on or checked bags. You literally have to pay for a non-middle seat, and pay to bring any luggage. Southwest has it figured out, and will continue to get my business. 
Too bad, I used to love Frontier back in the early 2000s and gave them plenty of support. They have chosen profits first over customers. If they did it the other way around they most likely would still be profitable.