Purely IMO, several reasons:

The primary market for Spanish SxS shotguns here in the UA has been the middle class. The low to mid middle class favored the less expensive box lock guns while the mid to upper middle class favored side lock guns. The middle class has been especially hard hit by the ‘recession’ (And I think the term depression is more accurate), and is having a hard time buying groceries and gasoline, much less SxS shotguns.

The Spanish gun makers, with their own set of problems, have needed to raise prices and drop the low end (“affordable”) models of shotguns. Add together more expensive guns and a market with less money and fewer sales are the natural result.

Another, wild card, factor has been the Spanish tax guns. About six, seven, years ago The Spanish government created a tax on the ownership of shotguns. It was a yearly tax, per gun. The result was thousands upon thousands of used shotguns were either sold to local gun shops or just turned into the Civil Guard. US importers (most notably CAI) bought and brought into the USA several thousand of these guns. Quality and condition was all over the place, but I was buying the equivalent of AyA No 1 or Ugartechea model 75 side locks shotguns, in VG to EX condition, for under $600 on Gun Broker. I was also buying, from gun shops in Spain, the equivalent of Garbi model 200 and Grulla Royal for between 1500 – 2500 Euro.

In short, that flood of tax guns killed the market for new Spanish SxS shotguns of all grades. Two years ago I was offered a matched pair of AyA No 1 shotguns for 12,000 Euro. The guns were made in the late 1950s, were absolutely top price point guns (they even had Purdey locks), and were in perfect condition in the original fitted two gun case. The guns were in Spain and I could have had the restocked to my measure by a Spanish gun maker for under 1000 Euro for the pair. At that time AyA wanted 15,000 Euro for a single No 1 gun, similar to but of lesser quality than, either of the pair from the 1950’s. Given that kind of choice, who in his right mind is going to buy the new gun?

These are the reasons, in my experience, why the Spanish gun makers are selling fewer shotgun today than they did ten years ago.