The datasets are available from the corresponding author on reasonable request.

Now look at what happens:

In summary, of 1792 e-mails sent, we did not receive any response for 1538 articles because messages were not delivered (N=77; 4.3%) or the author did not reply (N=1461; 81%). Responses were received from 254 (14%) contacted authors 

So, first of all, I am not sure that we should consider the 4% who did not have a message delivered considered to be "non-compliant". That is important as the headline number of  93% did not respond includes those who were not actually successfully contacted. Of those responding, about 1/2 (122 vs 132) shared their data. 

Then we have the most common reasons:

1. The authors asked for more information about our study, but after our detailed response and clarification, we did not receive further response from them 
2. Their informed patient consent did not include sharing data with other researchers, or the ethical committee prohibited external data sharing and use 
3. They cannot access the data, either because they are no longer in the institution that conducted the research, or they are no longer active on the project 
4. They do not want to share the data or in any way participate in our study without a specific explanation