New girls can be legends too especially when fans treat them like goddesses. Most girls join in the past more on the money side ignoring the other coercing cases since there was no social media and barely any events back in the VHS days. Nowadays, young teens see these av legends as their goals, so they join too. There are more ways to make money besides filming and event nowadays and it's not just sugar daddy or escorting. Even Aino back then like mihiro and okazaki find troubles in her gravure idol career decided to do av because it's becoming a norm and her starting salary was good, but she admit that she was inspire by rio after watching her av. She feel like she could be the girl next door angel like her and be successful too. Kana from ideapocket now also mentioned she idolize Aino. It's also a lot to do with fame and attention too even though it's av since most fans wouldn't be rude enough to shame their idol publicly at events. Yua mikami got a lot of gig going on after switching to av and use honey popcorn to draw more attentions. Other av idols uses their fame to star in movies or make good investments. You can say some really got talents without connection networks or no talent at all, but av allow them to act and sing on the side or after retirement. Of course, not all av idols are like that or can make enough money to retire in a few years.
I'm not sure about the turnover rates, but I assume there are even more girls joining av. It's kind of becoming a norm then. The av competitions is becoming as steep as regular gravure idols except the pay is still at least better in terms of debuting newbie for both side respectively.
1)I find that complete bullshit i'm pretty sure the majority of the girls in the industry grew up saying "I want to be a pornstar" They do it because it's quick cash, some become stars majority don't but it's quick cash.
2) unless you're at the top there is no money in Gravure, the money is in tv/movies, or Porn Sakura Aida, and Meguri where solid size and went to JAV not because they inspire to be like other av idols, but because of the money.
3)Aino was a star, who within the industry doesn't want to be a star, same when Aino joined she idolized Rio because she wanted to be a star like her because she was already in the industry
4)I don't get your Yua Mikami point, she was from the AKB universe, and she was originally one and done but her debut made a crap ton of money and months later she returned.
5)very few have that power to star in movies, and if so they are B movies, or tv stuff
6)very few get those opportunities, heck the Ebisu Muscats all the JAV actresses within it have been established, but there are many many many more who won't get those opportunities.
7) The nature of all porn in the world, very high turnover rate but a lot join each month, it won't ever become the norm but it'll always happen