I always ask this question.It's a good one😀
Whilst I think manditory family shunning is the big issue, being unable to leave on reasons of conscience, and still keep your relationships in tact, is at the root of the issue. This happened after they brought in shunning DA'd ones in 1981, following their unprincipled attack on Ray Franz.
Some people would say, and I think they're probably right, that it started when Rutherford brought in all those intrusive rules on what should be personal matters like health care ( blood, vaccinations etc) and grooming.
Not sure when all the silly chaperone rules started...or did they just carry over from the 1800's?? Its also very upper class - the poor didn't have time for such niceties.