I've never noticed any general dislike of 40SW, and I've never noticed 9mm being more available. In fact in my area, when I actually cared about what was available, 40SW was considerably more available than 9mm.
I personally wouldn't concern myself with why folks seem to like or dislike any particular caliber, nor would I base any conclusions on rants found on the web.
What I
have seen is a continuous parroting of "it's got more snap" and "it's just too snappy", all of which I find to be a rather tiresome repetition of what might be initial perceptions based largely on initial preconceptions.
I did read one lengthy explanation by what appeared to be an online 'gun writer' claiming he didn't care for 40SW "and other
high pressure rounds", but liked to stick with 9mm and 45. Apparently he had never browsed SAAMI recommendations for 40 and 9.
4. The .40 operates at higher pressures than both the 9mm or .45, which results in greater wear and tear on the firearm
Folks should really read occasionally, instead of repeating what they've heard. This takes a few minutes to research using Google, and would go a long way to improving the signal-to-noise ratio of firearm-related information that seems to abound with misinformation and poppycock. NO...it
doesn't operate at higher pressures than 9mm.
I personally think it's a short, ugly, weak little wimp of an auto pistol cartridge on the one hand, and one that's a pleasure to shoot and does about 90% of what 10mm can (with published loads) on the other.
I have found it to be a pleasure to handload, with good versatility in terms of low end to high end load, and it has even done well with 135 gr bullets and light loads, which makes it fun for IDPA and plinking. With 4756, I think it can be loaded hot and still perform well, and using 180s and fast powders I've even stumbled onto some remarkably accurate loads--that was using 'stumble' as an understatement. It has been a challenge to get good combinations that work well in certain guns.
I like it because it's dirt cheap to load, shares bullet choices with 10mm, and can pack a serious punch just as easily as it can support wimp loads that are fun and cheap.
Spouse just asked me today to buy her a carry pistol, and my choice for her would be 40SW...and I love her a lot. Far too much to give her a 9.
But I wouldn't introduce her to handgun with a little compact 40 loaded up with Gold Dots...that's just stupid. But it's not a problem with 40...it's a problem of giving the body time to learn...noise, recoil, flash. These can all be fairly severe with little compact handguns in 40. No different than giving a new shooter a Beretta Nano in 9 loaded with anything at all, and expecting the second shot to hit a target downrange. Not the way to develop an opinion on any cartridge.