Exactly. If the educator requirements were lowered or eliminated, the science teacher base from actual scientists would increase dramatically.
Education funds are for educators, not for educating
Also, older people who have not regularly worked with kids are nowhere near prepared for the energy level they will be thrust into. Most people at retirement age are looking forward to slowing down a bit and relaxing. Tossing them into a room full of volatile teenagers is the exact opposite of what most of them want. They tend to become very impatient and angry with kids and try to be the tough guy. If they last two years, it's a miracle.
Some men can't get along with their own 2 or 3 kids. Now imagine having 100 or more kids each day, whose personality is different every day, whose families are terribly screwed up, who don't want to listen to you, and you are in for the ride of your life. Also, most adults are not tuned in to the culture of today's kids. For older folks it is like being from another planet. They spend most of their time laughing at that stupid old fool trying to teach them.
These guys MIGHT do OK in a highly academic college prep school, but in an average or below average school you had better give them a year of observation of successful (and unsuccessful) teachers before you put them in a classroom. Most of them will probably drop out of the program. Whoever thinks two weeks of student teaching is all you need is insane. Bare minimum is working with an experienced teacher for a year and slowly being integrated with constant guidance into taking over teaching that class full-time.
How do I know this? Some years ago I was a teacher. I saw a number of these guys come and go, burned out quickly. After a while on the job, they came to the conclusion, "I don't need this." If you don't have the heart and energy of an enthusiastic kid in his 20s, think long and hard about "retiring" into teaching.