With HM Naval Base Clyde and Coulport employing 5,000 plus people, it's not exactly a priority issue. The SNP is anti-Trident in addition to being against the building of Nuclear Power Stations to replace Hunterston and Torness. The latter they can do something about but not the former as Defence is a matter reserved by Westminster.
The SNP has a Defence view for an independent Scotland but in practice is more interested on jobs and their impact on the economy. Either being pragmatic or "having been bought" but certainly within the remit of the Edinburgh Parliament. They can be vocal on the threat of closure to Lossie and Leuchars without facing the big "what if" question.
XV277 clarified the West Lothian question but who can suggest why HMG has decided to leave things as they stand?
In any event Tam's question also applied as much to powers ceded by Westminster to Brussels which have also reduced the power once vested only in those at Westminster.