I can only speak for myself here but... A lot of things are taught in school. Most of them weren't something that I use everyday and thus have forgotten about it (some more than others, of course).

Ohm's Law would've been taught to me sometime during highschool (as the other commenter mentioned, I can tell you it relates to electricity but without looking it up I couldn't tell you the actual principle behind it) - I graduated from highschool 10 years ago, and have not had a reason to "flex" that memory ever since then.

Great. So is history, trigonometry and literature.

It doesn't mean adults know it. Most of what you learn in school will be forgotten unless you have a reason to keep using it.