- It could be the organizational policy like individual appraisals and rating encouraging competition among the team members killing the team unity
- People related issues, like the command and control Scrum Master not letting the team to make decisions
- Tools and environment issues like the lack of automation and lack of skills in using tools,etc
We could list out many more...
I came across this article which lists 100 impediments that is constantly seen on Agile projects.
This website classifies various impediments into categories.