What is this 71% vs 20% notion all about? There are too few people to market products to as it is, so developers simply use the RISC OS 3.7 feature set. With RISC OS Ltd holding onto everything they've developed rather than making some of it backwardly available (like the nested WIMP) they've basically locked developers out.
As an example, look at NetSurf. Amongst other things, it has to provide support for PNGs that have alpha transparency. This is the perfect use for a new Select feature - but it can't be used as it alienates a huge percentage of users (and almost all of the developers). As such, a alpha transparency module was written, valuable development time is thrown out the window and another feature goes to waste.
As much as I respect the fact that RISC OS Ltd have to keep themselves afloat, there are some components that really should be made available otherwise developers will simply find their own solutions and RISC OS Ltd's efforts will be wasted. In my eyes this includes Toolbox fixes (as they have been - the versioning situation between OS5 and Select/Adjust here is a joke though), alpha channel sprites, and basically the stuff that affects developers and not users.