With my user hat on, I agree. My main workstation is still going strong with 10.11 (the latest it officially supports), and there's no end-user features of >10.11 that I want (maybe APFS). Or even of newer hardware.
With my developer hat on, I completely understand where they're coming from. Sierra adds a ton of useful new functionality, and fixes a ton of bugs. (There's several new features in 10.11 which just seem completely broken for any non-trivial use, and which were fixed in 10.12.) Not needing to support 10.11 makes life a lot easier.
If I weren't using 10.11 myself, I'd make my application 10.12-only in a heartbeat.
Might as well start thinking about upgrading anyway. If the past is an indicator, Apple will likely stop releasing security updates for El Capitan in a bit less than a year.
