Because your stand-up is a 45 minute conference call to India.
Because you still have to estimate total effort and duration.
Because the customer does not attend reviews or planning meetings.
Because you are not showing working software at the end of your sprint.
Because you are following an “Agile” process mandated by a central PMO team.
Because project priorities still change on a daily basis.
Because you don’t monitor burndown and feed back what you see into planning.
Because your team leader just assigned you a JIRA.
Because the definition of complete for the task you are working on is in your manager’s head.
Because you feel relieved when the daily stand-up is cancelled.
You are not doing Scrum. You are just spending more time on the phone.