Well that makes sense if the Deep State wants to stay deep enough to avoid detection, subs being so hard to hide from satellites ‘n all.
It makes total sense in as much as the dark side would have a hell of a lot more trouble acquiring a nuclear vessel AND non nuclear subs are quieter than nuclear due to not having cooling pumps in continuous operation. The main problem with non nuclear is that the best ones that don’t need to surface for battery charging only have a maximum of 20-25 days of in motion at 5-7 kts under water endurance. That translates to maybe 200 miles a day, 2000 in 20.
Given that, they would need some sort of cover to refuel unless they are on a 1 way mission and their origination point is within 2000 miles of a possible west coast target.