I'm not into Delphi or C++ so I'm no expert but the main issue is the 6 months wait for Mac version, Windows users don't see this, they just see what they get at xmas time and it works good for them, so why change ?
I just think implementing things would be a lot quicker and easier than Delphi, as you can see with the JUCE BBPLUGIN things get implemented quickly and look a lot better visually rather than taking a year in between each time that makes things very slow.