The relative paucity of actual oldtime musician albums (as opposed to bluegrass, pop or movie 'oldtimey' soundtracks, and country albums for example) has precluded actual oldtime recordings from becoming mainstream. One should probably agree on the definitions of both 'mainstream' and 'oldtime' when discussing it, since diff folks include or exclude various genres when referring to 'oldtime music'. (Most don't include the Southern harmony singing traditions such as Louvin bros/Stanley bros, or cajun, etc) The tunes Freeman refers to as obscure were indeed obscure...but... like 20 or 30 years ago. Freeman founded County Records in the early '60s, and County was the very first label to focus on oldtime music. This was before CDs and before most cassettes...only LP records played on turntables. Very few new records were pressed each year because they were a huge expense and investment.
But anyhoo... Almost all the serious OT musicians I've known have passionately dug deep into the 'roots' of the music (i.e. researching/absorbing from the older traditions and sources) while also infusing fresh life and their own personal approaches in playing the material, including creating new tunes..continuing to grow and explore as musicians as they get older.
I do find that unfortunate when any of those people who were responsible for hunting down and saving thousands of irreplaceable old family and field recordings that were rotting away in barns about to be lost forever (Bruce Greene's hard fought Salyer collection which he gave to Berea, Dwight Diller's Hammonds recordings..) are sometimes later portrayed as musicians 'playing the same old tunes' -as if they are stale or in a rut. These are the same people who at great effort wrestled some of the most obscure and beautiful music from the brink of extinction not so very long ago.
Amusingly, some of the 'source people' now mined by the newest batch of young musicians, were those very same young urban college-educated musicians in their 30s, making field trips, roughing it and getting excited by their own 'discovery' of OT music back then. Ironically, many did not grow up in the tradition, yet helped preserve and document some of it. They started the oldtime festivals that are frequently young musicians' first exposure to the music. Those players are now in their 60s, 70s, and 80s...recording incredible stuff of their own and teaching and passing on what they've learned from those before them. The good ones know how to pull something fresh and exciting from a tune whether they've played it ten times or eight hundred times.
Of course, the old must always make way for the young. Hopefully the young are insightful enough to learn from the generation before them who were certainly true music pioneers in their own right. O ldtime musicians young and old have been 'shaking up the oldtime movement' ever since the Highwoods and the NLCR (which is about when the only thing one might conceivably call an 'oldtime movement' may have occurred). I like to think shaking up is continuous, and ageless. :)
Those irritated by grain of sand best avoid beach.
-Strumelia proverb c.1990