Why are pretty much all white elite marathoners 2:12 runners?

HRE wrote:

Most people now get their best marathons in their first ten tries because they don't run many more than ten and run them so infrequently that by the time they've gotten to 10 they're late in their careers. Jack Foster got his best after eight years of running and he frequently ran 5 to 7 marathons a year. Ron Hill needed nine years to go from 2:24 to 2:09 and was running at least 2 marathons a year and often more during that time. The friend I mentioned earlier got his best time in his 97th or 98th marathon fourteen years after his previous PR. There are few things in life that you get better at doing by not doing them.

You mean, most people now like Shorter who ran his lifetime best in his 6th marathon? Or Salazar who ran his best in his 2nd attempt? Or Carlos Lopes who won the Olympics in his 3rd marathon and broke the WR in his 4th? Or Steve Jones who broke the WR in his 2nd? How many marathons had Spedding and Treacy run before the LA Olympics? Or you meant runners like Clayton and Peters?

Noakes lists only three major exceptions.

de Castella ran his best in his 13th, but he also broke the WR in his 6th attempt.

Ron Hill raced track and cross country frequently until he ran 2:09, and then got slower when he started racing marathons more frequently.

Bill Rodgers, who now says he would race fewer marathons if he could do it all over again.

Shorter said it was hard to peak more than once a year, and therefore gave it all only in the Olympics and Fukuoka. But he was a track runner who knew little about marathon, right?

Lots of people run their best marathon in their first few tries and then stop doing them for whatever reason. Shorter was starting to break down physically soon after that first 2:10. Rodgers had a tremendous career doing what he did, not doing what he now says he would have done. Hill was well beyond his 10th marathon when he got his 2:09. He was also a bit short of 32 when he ran it. He began racing marathons more frequently a couple years after that because he could make money doing them and considered himself past the point where he could be an internationalist at shorter distances.

If you don't run more than 10 marathons you don't know what will happen in your 20th or 50th but there are people who have gotten their fastest marathon after their 10th, often well after their 10th. There are also people who've gotten their fastest marathon in their first or second tries. But ALL of the people you mention ran marathons more frequently than most current top westerners run them. Kjell-Erik Stahl had run dozens of them before he ran his 2:10. How do we know what would happen if some 2:12-2:15 guys who run maybe three marathons in two years began running three or four a year? Doing that worked very well for guys like Hill, Foster, Stahl, Rodgers and now Kawauchi.

When Ståhl ran his 2.10 (1983 WC) it was his 6th marathon that year. The previous 5 had all been sub-2,15.