I will jump in being that I was baptized and raised in the Episcopal Church. As most answers to complicated questions are, there are nuances to the explanation from what I have seen in the Catholic Church. Now, I am speaking of the Roman Rite and not of the Eastern Catholic Churches (the Rites of the Melkite, Byzantine, Maronite, etc.), which is a pretty big thing. It seems to me that in all of the Catholic Churches there is a degree of “inherited faith”–you are what your parents and grandparents were. In my view, there are a great many “cradle Catholics” who were quite clearly poorly catechized growing up. The level of ignorance can be astounding. Many of them have infrequently opened (it seems to me), let alone, studied the Catechism approved by Blessed John Paul II in 1992. As a result, most of what they get about the Church and what she teaches is from the secular media or was during the key formative part of their lives. Because the Roman rite is so universal and is the rite of 90% of the world’s Catholics, the ill-informed Catholic can drift along and not be seen and not even be pushed to learn more about the Faith in all its beauty. Furthermore, when one sees that certain disciplines are relaxed (but don’t really comprehend the profound difference between a discipline and dogma/doctrine) one can see how the changing social and sexual mores of mainline Protestantism in North America, in particular, could seep into the collective mindset of millions of Catholics "by inheritance. In the Eastern Catholic Churches, though (perhaps because of their smallish numbers combined with ethnic issues), there is great emphasis on the Eastern Catholics learning THEIR Rites, traditions, devotionals, etc, as a way of maintaining their special identity as EASTERN Catholics. So, there tend to attend mass in greater numbers (by percentage, tithe more, attend more community gatherings, and LIVE their unique Catholic Faith more on a daily basis than their Roman Rite brothers–in my humble opinion.
For me, the Roman Rite Catholics fail to appreciate the beauty of their rite and importance of it in their daily lives. They have seen certain practices and devotions go by the wayside in the aftermath of Vatican II (or were never introduced to them at all), such that the Episcopal Church seems like the Roman Rite Catholic Church without all the “sexual hang-ups” and rigidity (perceived) of the Church hierarchy. Being good Americans, they like the prospect of the democratization of the Church polity and point to the Episcopal Church as a way of seeing it down in a reasonably acceptable “alternative” way to love and praise Jesus. Yet, they don’t cross over as much as the original poster is thinking they might. Why not? I think it has more to do with being Catholic by inheritance and/or culturally (being Polish, Italian, Hispanic, Irish, etc) and not wanting to change. I also think there is an inkling of underlying belief that the Catholic Church is special and that the Holy Father really means something, in addition to the Eucharist being more than just symbolism, which is what it is in many Episcopal communities (but, true to Episcopal tradition–you can find a few who declare they are Real Presence Episcopalians). It is the “remnant”–to use a phrase from the Prophets–of the Truth of Catholicism that still resides in them, so, they stay with Rome, even though they knowingly or unknowingly tear at the fabric of Church by erroneously thinking the Church is a democracy wherein some beliefs can be voted on by popularity or “reason” (in the post-1950s sense).
The solution? I don’t know but have some suggestions–get Catholics of the Roman Rite to better appreciate and love the Church, her history, her sacraments, her Catechism, her glorious devotions and pious traditions and bring back a bit more of the idea of being holy–set apart as Catholic Christians. Bring back certain old disciplines and educate them on why they were part of the Church for so long. Get folks to actually read the Catechism and Scripture more often. Teach more parishioners in the art of apologetic, with proper respect and charity–more so to better love and adore that which they have been gifted, perhaps without realizing it. If you do these things, perhaps more “cafeteria” Catholics will start to enjoy the menu prepared by Catholicism from centuries ago and keep the special of the day (or the decade) that the Episcopal Church is selling sitting off to the side. Blessings!