You can have an infection in say your arm that requires medication. The medication is on the banned list but it'd really sort out your arm problem. The arm issue doens't stop you racing.
To control usage of a possible performance enhancing substance.
Requested and administered by a medical professional within the WADA guidelines to deal with a medical issue vs. someone nailing a heap of said substance before a race to gain an advantage.
Really?
You can have an infection in say your arm that requires medication. The medication is on the banned list but it'd really sort out your arm problem. The arm issue doens't stop you racing.
Or TUEs for legit asthma or any number of reasons.
http://www.telegraph.co.uk/sailing/2016/09/16/i-am-not-ashamed-of-getting-an-therapeutic-use-exemption-but-the/