PE is indeed a science, but it is a young science. Yes, jelqing has been around forever - but the concept of a daily routine with warmups and gadgetry and cooldowns is all pretty new on the timeline, right? Therefore it will be dismissed out of hand (see what I did there?) by many people and most professional groups (ie the medical community).
This is part ignorance, part fear. It's so risky for those people to endorse any activity which carries a risk of injury, as it could be potentially career-ending for people in that profession. Ever since Andrew Wakefield made the link between Autism and Vaccinations, journalists and medical professionals have been extremely leery about speaking up, lest they be destroyed. Unfortunately until scores upon scores of tests have been done under lab conditions, do not look for the thumbs-up for PE from the medical community - even though I'd bet good money at LEAST one doctor has tried PE and gained from it.
Well.....all of that, coupled with the fact the Illuminati don't want anyone to have a bigger pecker, obviously