Because they don't make a huge amount and it is very popular in the US. They are not able to brew year round because it is spontaeously fermented, there is no refrigeration involved, and it is not a big brewery to begin with. (Most breweries that produce lambics and gueuze have limited output.) Also the gueuze production requires blending lambics, some of which sit in the barrel for as long as 3 years before being added to the mix.
I've personally never seen a pattern that is predictable in advance so you get lucky (or you go to Brussels where its just another beer and fairly easily found among the other brands of lambic/gueuze), or you order it from online shops such as belgiuminabox, etc., or you use online resources for finding the beer, e.g.: https://www.beermenus.com/search?q=cantillon Finally, you can go to a high end Belgian-style restaurant in the US where they have it on the menu. For example, Philly has multiple places, e.g.: http://monkscafe.com/bottles.cfm
^ thats not great news but oh well what can you do. I emailed the importers but they never responded. Probably busy scoffing at my noobery.
For whatever reasons Cantillion became very popular about 5 ago. Before that is was easy to get if you knew a store that carried it. A good friend of mine used to drink it all the time but has not been able to buy it for 2/3 years now.
Its the Pappy Van Winkle of Beer, dude! Used to sit on shelves collecting dust then someone decided it was the best shit in the world and now everyone wants it (including me!) I just scored my first bottle of Fou Foune in trade, I will let you know if its worth it! HaHa!
Cantillon: Serious Beer for Serious People! As a wholesaler I went from not being able to move Cantillon to having to split cases and parcel it out to pissed off retailers across North Carolina. I was always partial to the Rose de Gambrinus- a truly unique and lovely beer.
I have had Cantillon once...but had to travel to Paris to get it. Cave a Bulles had multiple bottles sitting on the shelves. Naturally I had to pay extra in baggage fees. Frankly it was one of my highlights of the trip. Paris is great but the beer scene is pure crap compared to most US cities. But if you like wine....
