The juice isn’t worth the squeeze to be a junior CA on the narrow body. The pilots peeling off for junior CA or WB FO means a new hire on the NB gets senior, and quick.

For example, an FO I flew with, who has been here for 2 years, already has a sweet schedule on the 737. 17 days off, good trips, some holidays at home, etc.

If he were to upgrade, it would be nothing but reserve or 90 hour lines with redeyes - for years.

If 737 CA paid significantly more than WB FO I’d understand. But it doesn’t. Why put up with the pain when you can hang out and really not make much less?