I similarly do a lot of documentation, mainly because it helps me to understand the scenarios and contexts, but also because I'm aware that it can short-cut the (expensive) learning curve for new hires.
But it's pretty universally un(der)-appreciated because there's no direct line from good documentation to "improved bottom line". I've not come across documentation-related KPIs, especially now that Agile gets misinterpreted as "no documentation" - sure, the code can change regularly, but the fundamental concepts barely change and should have a couple of levels of documentation (detail and overview) as they're fundamental to the business itself, and user processes change slowly enough that updating existing diagrams is a progressive, not wholesale change.
But it's pretty universally un(der)-appreciated because there's no direct line from good documentation to "improved bottom line". I've not come across documentation-related KPIs, especially now that Agile gets misinterpreted as "no documentation" - sure, the code can change regularly, but the fundamental concepts barely change and should have a couple of levels of documentation (detail and overview) as they're fundamental to the business itself, and user processes change slowly enough that updating existing diagrams is a progressive, not wholesale change.