There is a common misconception that ‘regular’ users drive adoption of such platforms. Really, it is what is usable in work and businesses what drives adoption. Of course, many are regular users, but what people use at home isn’t always a way to gain market share.
You are right, many regular users could get on perfectly fine with Ubuntu. Now more than ever since so many people just use computers for the web. For Linux to get in on business for (for employees desktops) they need those specific examples of applications, not the alternatives, because the transition process probably isn’t worth it for them, and often enough those alternatives don’t addess their needs well enough. If Linux could get in on desktop computers in businesses, then it creates a snowball effect which improves the position of the platform due to that new demand.
People can say they don’t need that, people are happy with Linux as it is, as a niche platform. But it’d be best for the industry, I think, if Linux was as good for all these different things so that we had a real alternative and the open nature of Linux would mean that it wouldn’t simply just a third player (or second, because if Linux did this, it’d easily take over OSX in market share) in the game, there would be an extra layer of competition hopefully driving innovation.