It's a combination of the other comments response about having to still manage state for invalidation and the issue with the none algorithm. JWTs specify the al

It's a combination of the other comments response about having to still manage state for invalidation and the issue with the none algorithm. JWTs specify the algorithm their signature was encoded with in the alg field of the header. There was a decent portion of JWT libraries that by default honored the alg : none. This would allow the algorithm field to be changed to none even though the JWT had a signature and the libraries would successfully validate the JWT.