This. For me, if not biblical, it was at least a real paradigm shift compared to any other closed-source DAW that I know of.
Some of decisive factors were customizability, extendability and relative openness - including REAPER not having any DRM. Whenever I think of something I might want to do in the app, there's probably already a script or extension for that - and if not, no-one is stopping me from writing/adapting one. And if I ever need to programmatically extract data from my REAPER projects, the almost-plaintext RPP format makes it relatively easy.
So far, any workarounds I've had to find (and any nitpicks still remaining) are insignificant compared to that. Plus, after version 6.3x, Razor Edit was a major improvement to manual editing workflows - after that, while I have other DAWs at hand, I've preferred to do most of everything in REAPER.