I agree. If you are not having even a single problem in your company which makes you wish you had an expert (not that all PhDs are experts) in a specific domain

I agree. If you are not having even a single problem in your company which makes you wish you had an expert (not that all PhDs are experts) in a specific domain (all the more if that domain is specialized in a way that you do not normally encounter in a typical software engineer job), it will be an unhappy marriage for both employer and employee.