Rebbetzin, there’s more than the boys’ maturity. There is the boys’ competence, and accepting of the need to leave full time learning sooner rather than later once you get married. Boys getting married earlier will lead to even more ridiculous support demands. The chassidishe boys may have more intense learning behind them due to non-existent English, and a willingness and connections to work in “business” that doesn’t require extensive training or schooling.
Now you can say, but the girls are older and have good jobs! Right. What if they want to stop working full time, or need to due to special needs kids, say, or have a complicated pregnancy? We can’t leave the burden on the wives and the parents! Parnasa issues can lead to serious shalom bayis problems and frankly, I don’t want to set my kids are up for this.