I've never been much of a fan of the VF series. VF2 is probably the one that I played the most but even when it was new on the Saturn it never really worked for me. My biggest complaint with the franchise is that so many things feel arbitrarily difficult for sake of being difficult.
A bit over a decade ago, VF4 was at Evo. My friends and I had watched the finals and thought the game looked awesome. We picked it up and played it a bunch for a couple of months. The Evo DVDs came out at some point so we bought them, watched them, and then realized the things we were doing weren't remotely as cool or interesting as what we were watching. Our interest petered out after that.
Years pass, I keep playing fighting games, I get better, and new VF games came out. With the fifth one I'm reminded of how I wanted to play VF4 back when so I invest some time and find out more about the technical nature of things like how damn near everything requires 1 frame precision, you have to do multiple option selected throw techs all the time to protect yourself, a couple of others that escape my mind atm. There also wasn't exactly a lot of local players when, at the same time, I could be playing SF4 with any of the 30+ people that would show up to weekly tournaments. So I didn't stick with VF.
BBZZZZTTT!
The correct answer is "because they switched to Tekken".
I could probably go off on this for quite a while. I don't think Tekken is any easier than VF in the end but when you're getting started? A lot of Tekken is readily apparent and you can understand what you did wrong by seeing it. In VF that didn't seem true. I couldn't just see a combo and copy it; combos were super hard and required a bunch of effort. Doing the things that I saw better players doing weren't feasible for me when I was actively trying to play the game.