Upgrade times
Imagine a 2-leg commute across the country. Would you do it, or would you wait until you can hold your regular commute base?
Suppose you’re in BWI, MCO or ATL as a fairly senior FO and you have younger kids in school and you have games and activities to go to. You hold whatever you want. You get your vacation choices. Do you upgrade and commute to OAK or LAX and go to the rock bottom of the list or do you hold out until you can at least hold a line in DAL, HOU or BWI? Or perhaps lance somewhere so you could theoretically drop your trips and pick up where you live?
Something else to consider... this isn’t a regional airline with regional pay scales where everyone is rushing to upgrade so they can get off public assistance and build turbine PIC time. Assuming you take advantage of your seniority living in base, is making extra 30-40k/yr worth the QOL hit that comes with commuting across the country and the loss of seniority horsepower that comes by upgrading at the first opportunity? To some it is, to some it’s not. I think there will always be bypassers, especially when there are seat locks involved.