Your question to me is pleonastic : of course, if you start from the idea that doping can give 4 minutes of advantage, you can ask "Why some of the athletes running 2:05 clean doesn't try to take EPO for running 2:01 ?" and your answer is "Because they are athletes for 2:09 clean, already doping for running 2:05".
My answer, instead, is very different : "Maybe some athlete already running 2:05 clean understands that with EPO can't have any advantage, and there is no reason to risk the career for reaching the same time you can achieve with training only".
You continue to show me examples of athletes having their PB when using doping.
Now, I give you some name who was doped, and AFTER coming back, with a high number of controls from WADA (always clean) was able to improve.
One example is WILSON ERUPE. He was caught for doping on 4th Jan 2013. In 2012, supposing he was on EPO, he ran Seoul Marathon in 2:05:37. Coming back after the ban, he improved his PB, again in Seoul, in 2016, running 2:05:13.
Another is MATHEW KISORIO, who frequently is used as example of the advantages of doping.
He was banned after a test in competition (National Championships) on 14th Jun 2012. At that time, he had 2 marathons only, 2:10:58 in NY 2011 (7th position) and 2:18:15 in Boston 2012 (10th position).
After the ban, he ran in 2:06:33 in Valencia 2015 (2nd position) and in 2:06:36 this year in Paris (2nd position), showing very much better shape than before taking EPO.
We start every comment from two opposite positions :
You believe not possible running fast without doping, and clearly overrate the effects of EPO on the performances.
I KNOW possible running very fast totally clean, and don't give any role of improvement to the blood doping, in spite of what some scientists can say after studying different level of subjects, of what you can think without any specific experience of training with top runners.
I also KNOW that, in more short distances, it's not possible to run at the personal hypothetical best (totally clean), reaching the same level of muscle strength they can reach taking steroids, and in fact when I speak about doping NOT WORKING I speak for EPO only, and not other substances.
The last thing, I want to reply that poster who calls me a lier when I say I don't want my athletes use supplements.
1) I don't see any ETHIC and MORAL difference between who takes an illegal substance, and who takes something legal, IF THE REASON IS THE SAME. Some substance that today is illegal, years ago was legal, and maybe in some year we can see at creatine, for example, like doping. If an athlete takes the legal creatine for having similar effect of steroids, I don't see any difference between him and who takes steroids, because HE TRIES TO HAVE AN EXTERNAL AID.
2) But I don't want my athletes can look at some external aid, that during their career can, step by step, reduce the self confidence, instead increasing the confidence in the medicine/supplement/product he uses.
3) The line between LEGAL and ILLEGAL substances is very thin. Athletes who were, at my eyes, without suspicions (for example Tyson Gay), in spite to have a scientific support (that African don't have), step by step went of the side of doping, because of the mentality to look everywhere for having some support. I don't want that a vitamin becomes multivitamin and then a mix of substances that is difficult to have under control.
When I was the Technical Scientific Director of FIDAL (Italian Federation), we had a case like this with Andrea Longo, 800m among the best in the world (1'43"74). Suddenly, and immediately before WCh 2001 in Edmonton, he was found positive for Nandrolone. He explained to the Federation that only he took BAA (aminoacids) from the top Company in the World (Ultimate) that was his sponsor. The Italian Federation spent more than 20,000 Euros buying the same supplement in more than 10 big European Cities, in different Countries, and sent all the supplements, in their original package, to the Lab of Koeln (Colonia) in Germany, for being tested by Manfred Donike, who was the head of the IAAF Antidoping.
After some months, we had the results : 27% of ALL THE SUPPLEMENTS WERE POLLUTED with Nandrolone.
Longo took 2 years ban, but he was recognized in "bona fide", and for him IAAF gave the opportunity to have still 2 weeks of time after the official dead line for the standards for WCh 2003 in order to run the limit.
Longo went in the Court against the Company, and won his trials.
The Company went to the Court with an allegation against unknown people for sabotage, for cleaning its image.
After that episode, I decided that NEVER my athletes had to take any supplement, especially in Africa, where the most part come from Asian Countries where there is not the MUST of listing all the components in the official way.