I don't want to denigrate the 1.4, I think it's good and it would be logical that everybody plays the last version of a game, but for some reasons a lot of people keep on playing in 1.0.
1- If you buy the game, it will be 1.0 for the most part (shops, ebay ...).
2- A lot of players do not even know 1.4 exists. Personally I discorved 1.4 1 year ago and I play wolf for 3 years.
3- A lot of people have issue with the punkbuster. 2 days ago I've helped a friend who wanted to try 1.4. He has a legal copy of the game, but it took 1 hour to fixe issues like 'game in failure' or 'client unkown toauth' and many others ... And you will see soon a new ECGN player
5- Even with a legal copy of the game, some people have the 'INVALID_CD_KEY' issue,and there is no way to fixe it. Some CD key seems to be corrupted.
4- A lot of people download the game, and it only allows 1.0 online. CD keys are from generator and aren't valid for 1.4.
5- Since the official downgrade patch came out, a lot of people stopped playing 1.4 for 1.0.
6- Several people like the 'drop-reload", a famous 1.0 glitch which allows a very fast reloading and makes a different gameplay. You can also disable it.
7- S4ndmod, a famous 1.0 mod, is daily updated and has some nice features like a 100 kb/s download (by default 12 kb/s), Punkbuster, and some other from OSP. It has fixed all old 1.0 glitches too, like the infinite nade glitch. I even see some graphics glitches in 1.4 I never see in 1.0 !
Anyway, when I search info about rtcw on the internet, people speak about 1.0 everywhere (videos, comments, discussions, servers-host websites ...)
In my opinion, 1.0 is more for the fun and 1.4 more for the tournaments. I play both and I find both awesome
And you may know this, but several ECGN players play both 1.0 and 1.4.
Sorry for by bad english, and I hope I've been helpful.