It is one of those "potty British things". Twin keels aka blidge keels work marvelously if your prime consideration is letting the boat sit stably on the bottom while a daily 20-foot tide runs in and out.
In parts of the world where there is only a single two-foot tidal rise (i.e. Florida) the entire concept of twin keels, which add lots of drag and cost and give you back nothing in return, is unheard-of.
And, outside of the UK and perhaps Nova Scotia, the resale value will be equally unheard-of.