Education and science are different matters. If you as a scientist want to spend time trying to turn lead into gold, then go for it.
I don't want my child learning that it may or may not be possible to make a perpetual motion machine.
If every time a teacher covers a new topic or theory in a science class they have to cover all the niche alternate theories, then the student is not going to learn much in the limited learning time available.
(That's not to say that there's not room for a separate "History and Philosophy of Science" module within a science class, but these topics might be more valuable when placed in historical perspective).