It's even simpler than that, if governments don't order ships skills atrophy and capability is lost.
Australia was building warships before and during WWI and almost stopped between the wars. An excuse given was how long it took to complete the cruiser HMAS Adelaide, but ignored that the delay was caused by the loss of critical imported components in transit during the war and then a slowdown imposed by the government post-war.
There was an enquiry, headed up by Sir John Monash into whether to build the desired County in Australia or overseas and the government decided to order them from the UK to save money. The irony is they then ordered a seaplane carrier locally, in large part to maintain shipbuilding skills, but then when replacements were needed for the aging out Town class, there was no recent experience in building cruisers, so they had to be bought from the UK.
It's a vicious cycle, when the government believe they are not getting value for money they starve local industry and buy from overseas, when they realise the full costs of buying from overseas, they set up to build locally, and when it costs too much they buy from overseas again. Worst of all, when local builds work and prove local industry is competitive and necessary, government often decides the new fleet of ships is more than adequate and stop ordering new ones, starting the whole cycle again.
