An OT has 4 years graduate school plus internships and externships. There are significant early barriers.
I think that in addition to that, it is not possible to practice without passing the exams, similar to doctors.
You can work as an accountant with passing the CPA exams and many do so successfully. You can work as an actuary (see DaMoshe) without passing the exams.
You are focusing on the wrong data in determining why certain fields have higher pass rates than others.
Excellent. Let’s get to Tachlis.
I’m not discussing “pass rates” (as you, DY, and others point out) as the only barrier. There certainly are many barriers for OT (such as a college education, a Masters, etc.) that most people can not obtain. Nonetheless, the field is more saturated and less difficult than a Doctor (even if both have a 90% pass rate on the boards). The “boards” and “pass rates” response was directed at Syag who brought them up.
One can work as whatever they want to, they are not a CPA unless they passed the accounting exams and have the needed education. If they call themselves a CPA (or actuary possibly, I don’t know) without the qualifications they can be sued.
If you with to bring up the Masters as the barrier to entry, we can have that discussion (and how much of a barrier is it as compared to other barriers, such as CPA exams, the LSATs, or the need for starting capital for a small business).