Linux developers are notoriously terrible at designing user interfaces. For example:
1. The Unity lens
2. GIMP
3. Open/LibreOffice
And those are the "big" applications. When you start looking at the smaller applications its gets even worse. Alot of half-assed, ugly looking applications.
Then there is hardware support, which they like to blame on the hardware vendors, but if you look at the poor quality user interfaces you can see that the vendors are only part of the problem. I'm not saying all Linux developers are lazy or poor at design, but that's what comes across when I use Linux applications. It's missing quality control and developers have no incentive to make their programs look nice.