With all the browser prefixes (moz, webkit, o etc) do they eventually get changed to the proper thing when the spec is finalized?

It's sad that, as mentioned in the presentation, CSS3 should reduce markup. but to do something like -moz-transition: 1s ease-in; -webkit-transition: 1s ease-in; -o-transition: 1s ease-in; transition: 1s ease-in;

What is there reasoning for not just doing transition, why do they all put their own vendor prefix on it?