This subject has been covered in past - In the boom years of the 1970s & 80s there were twice as many hire craft. Many of the large yards were taken over by the big companies ( Coral & Guinness and others) sold back when the bubble burst then lean years when economy & accountants came to the fore as in most business's
Economy of scale now rules aided by the growth of short breaks especially off main season added to the mix (the traditional Saturday to Saturday relied on a lot of school age staff being ) I suspect a bit of Health & Safety is involved (Qualifications to work on gas & other technical equipment also a factor)
All in with investment needed for what is still a seasonal trade the use of booking agents mostly investment companies not good old Hoeseason's & Blakes any more. Even the internet has totally changed the world.