I've had this happen to me at JFK arriving to the airport. Arrived to the gate (last one in T4) 15 minutes prior to departure and they were closed as the crew wanted to leave. It was the last flight out to my destination and entirely my fault for not getting there sooner as never should you be banking on T-15 as the law. E.g. if rainstorms/thunderstorms approaching/threatening and they want to go - they will go!

To OP - I think you are assuming you are that important to hold a flight with 90%+ are onboard and ready to back-away. If connection is late/close as you are sprinting across concourses.
If you are transferring a bag - there is NO WAY it will make it. If the pilots have their paperwork, take-off slot, flight plan holding it another 15-20 minutes can alter everything and place them further behind.
If you are elderly, kids, handicap - there is NO WAY you will make the connection between concourse to board the flight so they take off.

I think the only advice I would give you here - increase the necessary connection time at ATL as you have three references of missed connection at busiest airport in the USA. Instead of taking pictures and claiming victimhood, realize you are the one posting three different missed connections due to cut-off time. Instead, of repeatedly knocking on that door or playing roulette wheel I'd verify each trip allows minimum 2.5 hrs at ATL so if you are delays you still have time.
Alternate advice - connect at a different airport which is less busy.

I'm sure other FlyerTalk users can give advice on better connection airports instead of ATL, EWR, JFK, ORD.