I have my own way of seeing things...
I've gone through a lot of stages in the years I've been a gunowner.
At first, I liked the small calibers... .25acp, .32acp, .32H&R mag, .380, 9mm. I look back, and I don't really know why or how I got into pocket pistols, but that's just how it went for me when I was 21. Then I had an infatuation with 9mm for a couple years - any 9x19 or .380 was fine by me.
Then, through a combination of education, events and realizations, I got into the bigger calibers. The .45acp is still my favorite cartridge, and it probably always will be. For a while, I didn't want anything smaller... but then I got infatuated with the .357 Sig, and that just took me in a whole other direction. I bought a Sig Pro in .357 Sig, and a .40S&W barrel for it since the mags are compatible for both. I didn't like the .40 as much as I like .357 Sig, but it has it's place. I thought I'd never touch a 9mm or a .380 ever again.
Now I'm coming to the opinion that .380 is just fine for self-defense, and the bigger or faster the bullet, the better. I see them all as tools in a toolbox. The 9mm/.45acp is like a nice set of channel-lock pliers. Great tool. Might be the only tool you need if you're a plumber by trade, but other people need a few other tools for different jobs. That's where the .40, .357Sig, and other calibers between 9mm and .45acp come in.
It's fine to dislike them, you might not have a need for one in your life. But both the .40 and the .357 Sig are gaining in popularity for a reason... because they
do answer a question, regardless of whether or not you are the person who asked it.
.357 Sig practice ammo is hotter than the hottest 9mm. Defense ammo for the .357 Sig is just that much hotter. It shoots through barriers, walls, doors and glass with accuracy, and still gives excellent penetration on human targets on the other side. The 9mm and .45acp don't do as well in those tests with similar ammo. The .40 offers basically the same ballistics and performance as the .357Sig in a round that's nearly the as big as .45acp, yet the rounds are just small enough to fit 12 or 15 of them in a magazine - without requiring the user to posess huge hands. The .357 Sig is more fun to shoot than any 9mm I've ever come across, and so is the .40S&W IMHO. .40 and .45 make more devastating wounds than 9mm and .357 - but, it's all about preference, situation, etc.
Lots of civilian shooters, LEO's, govt. agencies, etc. are starting to prefer rounds like the .40 and the .357 Sig. I doubt that would be the case if they couldn't do anything a 9mm or .45 can't do. Remember - .45acp is my favorite cartridge as well. I carry a .357Sig because if I have to use my CCW, there's a chance it might be against a group of thugs in a car. When investigating bumps in the night, I grab the .45's or the .357 magnum. Until I get a .22, my 9mm or .38 Special is what I practice with. Once I get a .22, I'll probably carry my 9mm and .38Spl more on short errands to the corner store, light days, etc.
Different tools for different jobs.