IMHO: Yes, subs are great when you need people to constantly be looking over their shoulder and spending tons of money on ASW. They are great at interdicting logistical shipping too. But, they are really really bad at being seen (that's kinda the point), and sometimes you want a unit to be seen to force an enemy to dedicate forces to take care of it. Look at the amount of forces the allies dedicated to sinking Bismark and Yamato. In both cases a not insignificant amount was dedicated to taking down a battleship and even then in both cases not without either significant losses on the allies side, or overwhelming force and waiting for the battleship to be uncharacteristically exposed.

Surface vessels can also provide direct fire which is actually a lot cheaper than a torpedo. The cost of a 5" shell is something like ~20k (2k per actual shell + fuse which I assume is at least 18k) vs $5.39M(2022, source wikipedia) for a MK48 torpedo. 5" gun mounts are pretty much fully automated at this point, they have places for sailors for emergency... but on a NOMARs ship you'd just YOLO on that and use a simplified version without the manual backups for weight savings.

One of the coolest things about this is not this operating on it's own, but operating with a larger manned surface vessel or sub. They act as a cheaper and disposable escort for a much more powerful vessel creating a force multiplier. This is pretty much identical to the "Loyal wingman" that has been under development for awhile.

TLDR: there is value in having a ship being a visible target and having a gun. There is also value in having both NOMARs and manned ships working together.