Ideas can be Rejected:

This is another reason the employees hide their ideas. Most of the employees are scared to present their ideas to avoid the embarrassing situation if it is not approved or appreciated. So, as a leader you must be responsible to encourage your employee even if you dislike their ideas and if you want to tell you didn’t like their idea, you can tell it to them in a polite manner instead of bouncing upon them for the poor idea. 

They are not allowed to speak:

Most of the time, it can be your mistake of not allowing them to speak up. Every time your egoistic nature can avoid your employees from coming up with their own ideas. Knowingly or unknowingly you will be putting your ideas in front all the time and that makes your employees become lazy, as they think you are there to give them the work. So, at this time it is your duty to lead your team from the back and push them to give their own ideas as it makes them to think. As it is observed at present most of the employees come up in their professional life only when they are conditioned to think on their own.