This gives a different, if not more informative, take on the Seabee re-engineering for production (the prototype was conventional skin-and-stringers/ribs).
RC-3 Specifications
As to why the production engineering has not been adopted broadly:
While it never hurts to consider corporate or engineering inertia - "We know how to do it this way and it works - why change?" - my guess would be that in focusing purely on construction costs, the Seabee approach may have resulted in higher operating and major-maintenance costs. Possibly due to weight (compared with
competing aircraft).
Probably substantially cheaper to replace a damaged wing panel with flat aluminum skin, "shaped" by the simply process of riveting it to a curved rib, than to order a factory-formed unique wing piece. There may also be "redundancy" questions - the fewer parts there are, the more each one becomes critical - if it fails.
Because the Seabee was such a "niche" aircraft - personal amphibious flying boat - it is a bit hard to find a fair comparison. but an
unfair comparison would be to a roughly-contemporary Cessna 170. Conventional construction. Equivalent range and seating, but higher speed and ceiling, with 70% of the horsepower and 60% of the fuel consumption (C170 7-9.6 gph, Seabee 13.5 gph). C170 can carry the same 3 people (possibly more cramped) with an empty weight of 1250 lbs vs. 1950-2150 lbs for the Seabees. And if one
must add the feature of being able to operate from water, floats can be added to the Cessna - but the boat-hull is hard to remove from the Seabee.
One could also compare the Colonial Skimmer/Lake Buccaneer designs, which originate about the same time (1948) and use conventional construction.
BTW, I have always appreciated the simple engineering of the Seabee's main gear, compared to some of the complex folding "grasshopper-leg" contraptions used in other flying-boat amphibians.