Well put Huggy!
Truth is to fly part 121 for a major or regional airline you have to have to hold a current ATP certificate with a first class medical. That being said, you only really need to have the minimum qualifications (per the FAA, restricted or unrestricted) complete before you take your type rating checkride for the airline. The requirements that the general public see that airlines require are set up by an HR department. You're always going to hear of someone that "jumped the line" and got an interview because the knew someone in management without having an ATP. They still will have to meet the min FAA requirements for ATP. In the coming year the only way that all part 121 carriers are going to be able to get guys with ATPs are those who got them while at another airline.
Not that I don't agree with Huggy about the ATP being a great professional credential. Those same HR people are going to be looking at guys with 3,000hr+ mil guys and no ATP next year if they haven't already.
It's all kinda like getting a pilot slot in the Air Force. There are guys that have zero hrs and ratings while some are seasoned airlines guys with 2,000hrs+. Both get hired and are Lieutenants in the beginning.