There's more truth to what you say, than most union people will admit.
Over the last 20 years, they kept the status quo for those already in. During the sell out overseas, they negotiated to keep their wages, (fair) but sold out any future workers.
My wife has worked at the USPS for 18 years 6 days a week for a total of 35 hrs a week. She was considered "part time" and has NO benefits other than vac. and sick time she accrued but wasn't allowed to use. now full time is 5 days a week, and as little as 32 hrs a week. She was in the union that was supposed to represent her. She asked at a union meeting why the disparity. A full timer said they were unwilling to give up anything for the part timers.
Hmm, 20% is full time 80% is part time. I suggested she quit, and as last week, she is now retired.
More unions over the years are learning very well from politicians on how become corrupt and self serving, screwing the workers in the process.
No wonder it's harder to find good people to join the unions. Pay dues for no representation.
The US Post Office is not alone in this practice. John Deer is another one.
If I remember my schooling, a revolution started that way over 200 years ago.
Time for a repeat ?