I doubt a great majority of people have a computer hooked up in their main tv room? Maybe they do, but I doubt it. You say just use a laptap. Sure well froget the part that maybe I'd want my laptap on hand while I watch the episode of say Damages Season 5 that my family wanted me to download and stream for them. I don't think it's that unheard of using a device like that while I watch tv.
So use a smartphone, tablet, or any other device that would let you do that? Or do this
crazy thing and actually just sit there and watch what's playing for a bit?
Damages? Wouldn't a show like that be up on Hulu, Netflix, or whatever to watch?
The point is, consoles are trying to be the this all in one media device. It would be pretty convient to have the PS3 just stream mkv files. I wouldn't have to unhook my computer and hook it upstairs all the time and my family would got more use out of the PS3 because they could just stream stuff from their computers.
IIRC .MKVs are not an officially supported format or recognized standard like .AVIs, .MOVs, .WMVs, .MP4s, etc. are.
You could always shell out $50 for a Roku player- I don't think you can stream .MKVs to those either, but IIRC you can hook up a hard drive or flash drive and watch them via a USB connection.
And again...why are you downloading .MKVs of everything? Have you looked for other formats? Do you know there are programs you can use to convert .MKVs to other formats out there too?