Ah, that's an easy one to explain. This thing started out as a hobby (actually as a project to learn to program in C++). At the point when I decided to make it paid, I left the free stuff free and only made things that I have added after that moment paid. Among others to get a huge user base (which is REALLY helpful because a lot of the suggestions for improvements are coming from free users), and to enable people to keep updating to newer versions so improvements in the sound will reach all of them and not only those that paid. That's basically it...
O, and also: Because I hate to have to pay for software
So I tried to make a distinction between features that you need when you're just listening at home, and those that professional users will need.