Besides Tourist, airlines want experienced pilots not just for their flying skills, but for command and decision making skills...
Airline flying isn't just stall avoidance and engine failure at V1... After the safety aspect comes comfort, economy and so on. A spotty 25 year old just ain't as good at that kind of stuff. Happily I was bashing the bush at that age in Barons and Islanders and learning the FLYING part...