Debian releases are supported for about half the length of RHEL releases overall, LTS included.
Debian “Stretch” for instance was released in 2017 and support ends 2022, so a 5 year cycle.
RHEL on the other hand has a 10 year cycle, and offers extended support beyond that:
“Red Hat Enterprise Linux Version 8 delivers a ten year life cycle in Full Support and Maintenance Support Phases followed by an Extended Life Phase.”
https://access.redhat.com/support/policy/updates/errata/#mas...
With Debian upgrades are realistically being planned every 2-3 years as the release approaches LTS.
That makes for a lot of extra upgrade work (about 3x more) when compared to the 10 year RHEL life cycle.
Exactly; almost nobody wants to maintain old versions like that. For most people, the fun part is writing new stuff, and maintaining old stuff without breaking backwards compatibility is particularly annoying to put up with. I certainly couldn't blame anyone, particularly who was just publishing software for free, for not wanting to deal with all that.