In spite of everything you've done for them, eventually they will hate you. Why bother?

Being a supervisor is really not that easy:

• Your subordinates does not understand that you are just doing your job so they keep on complaining about you being strict. I guess some cannot differentiate the word strict from the word professional.
• Whatever wrongdoings your subordinate does will reflect on you! You are the one who's going to explain to the manager about what happened even if you're not the one who did it!
• Coordinating issues with other departments for whatever your subordinates need is not a good experience too.
• Administer HR and Department policies as instructed.
• Identify performance gaps and prepare action plans for effective coaching and performance.
  

ALL THESE AND MORE! AND YET THEY DO NOT APPRECIATE THE LITTLE THINGS THAT YOU HAVE DONE FOR THEM (as if they are giving you the numbers that they should be achieving!).