I work for a company operating under part 91 (general operating rules as opposed to charter or airline) flying King Airs. We had one captain who was determined to skip going to the regionals and instead to go directly to Southwest. After long enough of not getting the job, he came to the conclusion that in order to get to the major airlines, the only way is through the regionals, and I must agree that for most of us, that is the only way a major airline will hire you. It is not just a matter of speed, but also making your career happen at all. Also, the pay is a huge factor in everyone wanting to get to a major carrier as quickly as possible. When the regionals keep pay low, that keeps pay in the whole industry low.