Why do the MySQL bin log files still exist after a purge or flush?

Question

I've used PURGE BINARY LOGS as well as FLUSH LOGS, but the mysql directory still contains these files:

mysql-bin.000025
mysql-bin.000024
mysql-bin.000023
mysql-bin.000022
mysql-bin.000021
mysql-bin.000020
mysql-bin.000019
mysql-bin.index

Is there a reason why using the commands are not working? These files are taking a lot of space. I would like to get rid of them safely.