Adrian Allan wrote: ...I think you mean, why is all contemporary playing free stroke?
1. Because all of the guitar repertoire can be played without a single rest stroke
But not played as well.
Adrian Allan wrote: 2. Rest stroke is stylistically wrong in anything before the Romantic period
"Style" goes to interpretation appropriate to the period, not the technical means of realizing that interpretation. And, there was not monolithic consensus as to as to all the details of either interpretation or technique in any period, anyway.
Adrian Allan wrote: 3. In the hands of a less experienced player, it can stand out too much above the free strokes, which is the default way of playing the guitar
That is diagnostic as to what needs to be addressed in practice by the hypothetical less experienced player, and is not relevant as a criticism of the technique per se. And, though free stroke may statistically predominate in application to the number of notes played in some randomly selected page from the repertoire, it is not thereby "the default way of playing guitar". Ii's contextual. If any particular passage lends itself to application of rest stroke as a technique, then rest stroke is the default technique. As for default technique in beginning and intermediate tutelage, one of my early, and better, teachers instructed me always to use rest stroke except in any instance in which there is a specific reason not to do so. I have long since taken a more relaxed view to this, but this was good training, and, in that phase of my training, it was rest stroke that could have been termed the "default" technique.
Adrian Allan wrote: 4. Arguably the man with the most perfect technique on the planet hardly ever uses it - John Williams
Four good reasons.
Of all the times I've seen some player forwarded as an exemplar of all free stroke only playing, this is the first time, and a surprise, I've seen John Williams suggested as such. It seems out of place. I don't believe this is so. Rest strokes typically abound in is playing, when and as is appropriate. As to the more usual suspects who have been conscripted into service, in the legions of discussions that have taken place on this topic to serve as representatives of all free stroke playing, it always seems to turn out upon examination that any one selected player of this supposed ilk is someone who doesn't use rest stroke except for when he does.
To the opening post: guitar technique consists of a great variety of alternate approaches and myriad possibilities in how to to do things, any one of which takes some time in which to develop an intimacy of rapport in using it. Of alternate approaches, don't defer working on one until you feel you have "completely mastered" another. You may get better and better, and feel satisfied at having made progress, but you also may find that you never reach the end of the road of attaining to a "complete mastery" of anything. That is a life-long journey towards an ever receding and ever re-defined goal. Teachers may differ as to what may be their very first starting point, but such priorities are generally pragmatic and fleeting. Once you've had your introduction, work on the whole package from the beginning, to absorb given techniques as autonomous responses delivered simply as articulations of how you want the music to sound, not as a series of hyper-conscious decisions made as selections from a technical catalog.