This is an interesting question that kind of assumes I've actually tried all these other media and made an informed and intelligent decision to go with one over all the others. Which, in my case, isn't true at all. I have never used either acrylics or oils. I have never been tempted to try them.
The "immediacy" of pastels is crucial, essential. I have my best luck and the most fun with processes that are as close to hands-on drawing mark-making as they can be. I have messed with watercolors and do play with gouache (and am just beginning to learn about encaustic), but the intervening brush seems to give me some trouble. I suspect that this is just a dodge, and that with practice, I might get the whole "brush thing", but hey-ho -- I just am not motivated.
I took an abstraction painting class this past winter and I was the only one in it using pastels (which had the unexpected advantage of no one wanting to share a worktable with me) but was tickled to be able to watch these acrylics and oils artists at work. To get a close-up and continual view of folks "working" those media. To see if I developed a hankering to try 'em. And the answer was 'No'. Still [shrug]: no interest.
The soft pastels are just so beautiful, so tactile, so right-away, so direct. Pick one up, lay down the color, and there you are. No squeezing something unseen out of a tube. No endless fussing with mixing. Nothing but the pigment and your own fingers/brain. I love the instantaneousness of it.
(I also have the luxury of not being forced to sell my work to live, so I don't give a hoot about framing pastels and all the attendant issues there. Particularly the expen$e. But if I had to make my living as an artist, if this was a job instead of a lark, I might think about making pastels for the love of it and making something else to sell.)