I have been a TA at two schools in the past and loved my job with the children. I left because of the staff who dragged everything down, hated the kids, treated them with utter contempt and threatened to leave every single day (never did though, most had been there years - wonder why).
Have you not seen the statistics about the number of people quitting the profession and the utter failure to recruit enough trainees year after year?
People can call teachers moaners as much as they like, but the stats speak for themselves. If it were a nice, manageable job, it would be easy to recruit and retain staff, wouldn't it? Maybe your school is the exception, and teachers aren't leaving. That doesn't change the general situation though.
Don't get me wrong, I have no desire to be a TA, but the relationship with the students is different when you are held directly responsible for their progress and eventual grades. Slogging away trying desperately to make interesting lessons to engage them so they don't fail is soul-destroying when it's constantly thrown back in your face and all you get is disruptive and abusive behaviour and no shits given about their own grades.
I'm lucky enough to teach in a lovely girls' grammar school now. Workload is still a bastard, but at least the kids behave.