That's the root problem, though, isn't it? It's a business/people problem. You won't have consistent UIs as long as software vendors consider look&feel as something to exploit for branding or competitive advantage. Since user feedback is rarely sought and routinely ignored in computing, you'd need the OS vendor to either disallow UIs not conforming to system theme, or make them impossible (by taking away the API for per-pixel drawing). Neither of those options is likely to happen.
Back in the XP days, there were generally two kinds of UIs: the ones that used the system theme, sometimes as much as trying their best to apply it to their custom controls, and the ones that disregarded the system appearance altogether and drew everything themselves, including the window borders.
> Since user feedback is rarely sought and routinely ignored in computing
This needs to change, too. I collect user feedback and act on it and my users love me more often than not. The world would be a better place if everyone was doing this.
That's the root problem, though, isn't it? It's a business/people problem. You won't have consistent UIs as long as software vendors consider look&feel as something to exploit for branding or competitive advantage. Since user feedback is rarely sought and routinely ignored in computing, you'd need the OS vendor to either disallow UIs not conforming to system theme, or make them impossible (by taking away the API for per-pixel drawing). Neither of those options is likely to happen.