They generally don’t like it, but a refusal is absurdly ill-tempered if the player owns an extension and the Low A is approached in a reasonable manner. If they don’t own an extension, there is room for discussion as players then have to make their own. Still, much of Mahler and Wagner include low A’s, and although Heckel no longer sells a “A bell” (as far as I know), low A’s are still performed. However, the extension is best used when inserted for the shortest possible amount of time as it makes certain notes difficult to play (and makes the Low B-flat basically impossible). Personally, I avoid the low A, but one should not pretend they are not played, because they really are. If both bassoonists in - of all places - the Red Deer Symphony own a low A tube and use it, I’d have to say it’s used elsewhere!