Well,
I am by no means any kind of refrigeration guy but I know that whenever a system is checked by the pros
, I know the first place they "Bubble" check is the fittings.
Now this is only speculation but I cant help but think that many AC manufacturers expect that their units will "never" need re-charging.
I suspect that there is a nominal savings with no fittings.
And if there are no fittings, the user would surely need the services of a Professional who had knowledge of sweating fittings and recharging (gotta keep it in the Clan)
But I guess the user friendly "pierce type" connector was not familiar to all who seeked AC assistance.
IMHO