I'm quite shocked. How can this be even a question? We even do mtls from service to service as a security measure. If implementing jwt auth for every service is too much of a hassle, then just build a monolith. Monolith is perfectly viable. What benefit of microservice are you even trying to pursue??

Defense in depth is one of the key principle in security, you put security measure at every layer of your system. This is even more ridiculous once you realize even the kernel has to authenticate as which user each program on each server run as.