scdaemon keeps the smart card reader powered on indefinitely
After scdaemon manages to find and use the card inserted to the reader, it prevents pcscd's idle timeout from working correctly, leading to the reader being powered on indefinitely after first successful use.
This doesn't happen when the card is not there or when the reader isn't operational (for example due to lack of valid firmware) - if scdaemon fails, pcscd shuts down after a minute of inactivity correctly, powering the reader off as well.