Top impediments to Agile adoptions that I've encountered

• Organisational structures, systems, policies were not updated so the change did not spread nor survive beyond the influence of a few key individuals
• No clear goal for adoption... especially no clear goal that connected with the strategic direction of the broader organisation
• Most software delivery capability had been outsourced which meant the organisation had generally lost the ability to judge the effectiveness of software delivery
• Not enough coaches available that were skilled across all the roles
• Instructors / coaches did not, or were unable to, convey the rationale and underlying assumptions of an Agile approach
• Agile cultural assumptions directly conflicted with the existing organisational cultural assumptions