Unlike in Europe, we here in Canada and the US have to work our way up to jets - we don't just come out of Flight School going to Air Canada, Delta, United, WestJet, etc. We have to fly something smaller to being with, something like King Airs, MU-2's, up through to 1900D's and Dash 8s, then if lucky you get to start on an A320 after 10 years in the industry - and thats if you are hard working after 2 or 3 years on the ramp slugging freight around. However, I digress.
For quite a number of operators, insurance is the answer. Its not that its unsafe to have a "200 hour wonder pilot" in the right seat of a 320 or 737 - it can be done safely, and has been proven time and time again for a number of years - but should there be an incident it will be the experience that counts, and from an insurance standpoint 200 to even 1500 hours is a severe liability for jets. At the end of the day all the simulator training in the world does not prepare you for the first time the engine stops, 1 hour from the closest suitable landing point, at night in a dark cockpit - experience does that so that the next time it happens you know what emotions will come into play (and the scenario I am speaking of is from experience - same route, same a/c, same crew, 6 months apart. Turned out to be a faulty fuel filter with an unassociated failure of an ECU.)
At the end of the day there is no regulatory difference between a low cost operator flying an A320 and a major, international airline (Emirates, BA, Singapore) flying an A320. The regulations (as they should have taught you in school) are based on the aircraft type, not the operators business plan.
My suggestion to all low time pilots is to go out and work the real world for a couple of years. This means working the bush in Africa, the Pacific Islands, northern Canada/Alaska, etc. Work your way up - trust me, your career will end up being long and boring if all you ever fly is long, international routes, ILS to ILS and hoping you fly enough to meet the minimum currency requirements.