Why does Chrome still use prefix for animations?

问题:

I'm really not sure if this question should be here, if not, please forgive me, but I'm intrigued in the reason why Chrome/Safari still prefix CSS3 animations, given that any other major browser supports them as standart, some even since a long time. (IE +9, Firefox +15, Opera +12.0 according to this)

@keyframes anim{}
@-webkit-keyframes anim{}

div{
    animation:anim;
    -webkit-animation:anim;
}

Is it still considered an experimental technology?

Thanks!