SIC time is necessary experience in order to be a better PIC in the future. If I am hiring a pilot, I want to know that person is reliable and capable of operating an aircraft. Having a lot of hours of SIC time just means you have a lot of experience watching someone else make critical decisions.
While I agree, just because someone has passed a PIC type ride doesn't mean they are reliable or even capable of operating an aircraft. I can think of one recent accident near BUF in which that was definitely the case. You are correct about the PIC and SIC time and experience, however, you need to start looking at it from the airline's point of view. If I was a hiring manager at JetBlue, Spirit, or Virgin, I would tell my HR folks to only call pilots with 0 to less than 1000TPIC time. You know when this economy turns better, a lot of guys with 1000TPIC or greater will want to bail to bigger carriers like SWA, Fedex, AA, etc.
By locking in guys with less than 1000TPIC, a LCC carrier can ensure these newhire pilots will not bail out to UPS, Fedex, SWA, etc.