At least part of the reason for this was likely that standard development practices, at least while I was working on Harmattan, involved a lot of reflashing. Daily, or more often, depending on how often you were multitasking in some cases. I was pretty resistant to this, but especially earlier on, it was hard to avoid.

Jolla on the other hand has been much more focused on getting upgrade paths working from the start. I reflashed my N950 a sum total of, I think 3 times, from when I started hacking on Sailfish in 2012 to when I retired it mid 2013. My Jolla devices have been a similar experience: I haven't often managed to get into a situation where I need a reflash, and when I have, it's generally been thanks to me doing something stupid not that I'd ever screw up my homescreen without USB rescue mode enabled, or anything..

This isn't to say that we're perfect, I'm sure we've made mistakes, but just that at least for a number of us, updating is a core part of how we work - not reflashing - and if the upgrade experience isn't smooth, we'd like to know why.