That is the essence of the whole issue. For the Protestants who are "their own popes," a thorough understanding of the Scripture in context and culture and language in which they were written would be a requirement. Plus, one would have to come up with all the arguments and counterarguments accumulated over the past 2,000 years — all on one's own and all in one's limited lifetime!
It's like trying to be your own master electrician, carpenter, architect, builder and computor programmer, speak three languages and hold six doctoral degrees all in one!
Liturgical Churches have retained the collective knowledge and understanding of the Scriptures which one single person can only approach at best with extraordinary effort.
We know that Catholics/Orthodox do not read the scripture as much as the Protestants. But their participation in the liturgical life is scriptural, without being formally theological, and without creating a 'personal religion' our of a personal relationship with God. We can always go back and check how the Church handled a particular issue, in context and in the cultural milieu of the times.
Protestants, on the other hand, search and pick here and there, trying to piece together the puzzle, often confusing, as jo kus aptly pointed out recently, personal opinions with the Holy Spirit. In fact, so many of them seem to equate, personal opinion with the word of God.
Right on, just what I tried to say in my previous post.