Actually I think it is all down to marketing !
Holland & Holland could not actually make a decent O/U thirty years ago so they commissioned David Dryhurst and Richard Tandy of W W Greener to make a number of prototypes , then they got Perazzi to do something similar before they went into production with their modern day O/U which in my opinion at the beginning was frankly a disaster.
We the shooters and our sporting magazines promote the O/U and popularise them , but frankly there is nothing better or finer than a nice SxS but unfortunately we do not promote them.
Put on a serious SxS competition with good prize money and watch the SxS flourish.
Without doubt Arrieta make fabulous products , but without demand and promotion we have no market.
IF sporting writers were to promote the use of SxS and extolled the virtues of SxS's there could be a rush to bring them back.
Sadly most writers are now wet behind the ears young knowalls with no original ideas and only prepared to play to the piper's tune for a free day shooting or an all expenses paid bribe.
All this may sound like vitriolic rhetoric but I can assure you corruption is alive and well in journalism.