It is my understanding that many wards grapple with the difficulty of the young men, in particular, fully intending to serve a mission while in high school but then enjoying a year of college or other pursuits and thereby (so the logic goes) becoming distracted from serving a mission. Shifting the age to 18 may be a way to help the young men “keep on track.” Now, we can debate whether their effectiveness at this lower age and maturity level will be as great for the missionary work as otherwise. In some instances it will most certainly decrease efficiency. But I wonder whether the net result, at least in the life of the young man and his later sphere of influence, will still be positive.

As far as your example regarding the young men who chose to serve at age 22 or such, it does not surprise me that they were held in such high esteem. But I wonder whether that is simply a question of maturity level generally, or rather a reflection of the fact that these young men, having so much time to consider and weigh other options, still chose to serve a mission. And, most likely, farther removed from the influence/pressure of parent and family. I think their spiritual maturity in still choosing to serve was a very strong factor in their missionary service. That does not answer the question, though, regarding the young man who waits a year and chooses to not serve a mission at all.

I also wonder whether that is what is going on in the bishopric’s minds in those situations you mention where it sounds like they are now advocating 18 as a hard and fast rule. Perhaps we are only hearing part of that conversation – in council they are weighing/discerning the spiritual needs of the young men in the ward, but in public it only comes out as a hard-and-fast “get them out at 18.” No clue whether that is true, but it wouldn’t surprise me.

Besides, Are you assuming that there is a default at all? From my reading of the announcement, it could be simply interpreted as “let’s start considering a mission when a young man is 18, but if he doesn’t want to go yet or priesthood leaders determine he is not ready, then a later age is still wholly appropriate and sometimes the better option.”