Basically, the PTA at my kids' last school was fed directly by the NCT
It was the same women who had eyed each other up at baby group, decided that they had enough of a shared interest in fabric samples and cupcakes to base a friendship on, and proceeded to clique-out the rest of us through the toddler and nursery years. And then, en masse, like some enormous hive, they joined the PTA. They set meetings at stupid times, mainly gossiped through them, whinged about how no one else came but were really unfriendly to those who did. They were nightmares, basically. To be fair, they ran a tight ship and did a good job and were fine as long as all you wanted to do was show up and look after a stall a few times a year.
I've also had the experience of a really different PTA, at a v low budget private school, where meetings were at a proper time, childcare was actually provided for them, and various rota systems were put in place to encourage everyone to volunteer. Eg a particular class would run particular stalls and a sensible time would be put aside for the class parents to get together. It felt very, very different.
What I really need, as a working parent, from the PTA is to be told what to do. Give me a list of things that need doing on fete day and I will do them and I will do them well. But if all you have to offer is gossipy meetings that don't start on time-well, I just cannot do that. Because I have to work, to pay for those bloody fetes.