So many PhD dissertations are worthless junk anyway. Things like… The effects of Shakespeare on the writings of Coleridge ….. Such a dissertation will be published in a professional journal and then will never be read by anyone but perhaps another English professor who teaches Shakespeare.
People get them not because they are worth anything or make you a more capable teacher but because the education system is structured such that you need the credential to rise in the education hierarchy and make a higher salary.
The do not make you a better professional, they just make you higher level, better paid member of the education establishment with a bigger ego and sense of self worth.
Just look at Dr Jill - she is the poster child for the EhD. .