When there is no feedback positive and/or development, my perception is that my boss does not care, yet it can also be that they are concerned about how you will react. Either way not getting valuable feedback is not good for your own personal development! 
My business coach has a saying “never die wondering” in other words ask the questions. So ask for feedback, what are my blind spots? what are the two things I can do that would make a difference? When you ask make sure you follow up in a note and share your appreciation for sharing the feedback.
If someone cannot think of feedback or it is uncomfortable, then seek to understand, why are they uncomfortable? When you know they are uncomfortable put them at ease, so they can be more transparent with you. Use phrases I appreciate feedback as without this valuable information I cannot grow. Here are some examples of areas of self development I am working on and then explain the focus areas IE attending Toastmasters to develop public speaking, working on better coaching by asking more questions. In most cases Leaders who are uncomfortable giving feedback the reason is due to have what is in their perception is the difficult conversation.
You cannot develop if you don’t know what you need to develop. Don’t be held back from your ambitions and goals because you work for someone who is not comfortable having the frank conversations.
A great interview question for perspective employers “what are you working on for personal development right now?” “What book are you reading?”. If they don’t have an answer, they are unlikely to be able to help you.
Angela Lovegrove 