Well, I think the apostasy which we see these days has influenced that. Great many cradle Catholics have abandoned the faith, while the converts from Protestantism usually decided to convert after carefully studying the Bible, Church history, writings of the Early Church Fathers etc. (see the conversion stories of Tim Staples, Frank Beckwith, Robert Sungenis, Jason Stellman and many others) - as a result their knowledge and understanding of the Catholic faith is often miles ahead of an average Novus Ordite. Some of them even become Traditionalists, for example Robert Sungenis and Gerry Matatics. Surely, there is often some Protestant mentality left, which I suspect is one of the reasons why the ex-Protestant, now Catholic apologists of Catholic Answers (Tim Staples, Jimmy Akin) completely collapse on the issue of EENS - this doctrine of exclusive salvation is radically opposite to the Protestant ecclesiology which assumes existence of "invisible Church" made up of believers materially belonging to different Churches or denominations. As a result, even though they have rejected heretical Protestant ecclesiology, I guess it can be hard to fully accept the strict Catholic salvation dogma.
Myself I'm a revert from Evangelical Protestantism. I was baptized in the Catholic Church but I fell away early (I became practically agnostic) and when I made friends with Protestants after moving to the UK I was ignorant of the Catholic faith and I did not know how to defend it. As a result I was initially convinced to the Protestant doctrines and joined a conservative (5 solas, T.U.L.I.P.) non-denominational Evangelical church. However, studying the Sacred Scripture, the Early Church Fathers and investigating doctrines which divide Catholicism and Protestantism led me back to the Catholic Church. Ironically, joining the Evangelical congregation eventually resulted in restoration of my Catholic faith and grasping much better understanding of it (God's grace can work in very unpredictable ways!). I suspect this might be the case with many converts/reverts.