If they're "good", they'll be up on PR2.0 (what doesn't have a 2.0 version these days? lol). Otherwise, they're living in a box. SEOs wouldn't be doing nothing but press release optimization. Keep in mind that many PR firms are joint firms (marketing / PR, advertising / PR, etc.), so they're dealing with other marketing issues than just PR. A PR person isn't going to be doing on-page optimization or anything like that, whereas many larger firms are going to require people with those skills, because they're not exclusively PR firms. That's the difference. But like I said, any good PR person will know how to optimize a press release. It's a part of their job, and a part of the industry. However, just because there's something new to add to the mix, it doesn't mean it's more important than the primary purpose of the tool... it's just an added thing to think about with added perks if the release is handled correctly in the first place.