The notifications are part of the admin. PW doesn't get involved with your front-end output, so it's not attempting to provide anything with regard to notifications on the front-end. However, you can still use the API to add notifications to any user, but they'll need to go to the admin before they will see them, unless you provide your own output code on your front-end.
If you wanted to output notifications on the front-end of your site, it would actually be as simple as this:
foreach($user->notifications as $no) {
echo "<p>$no</p>";
}
There are of course several other properties, methods and flags that you can access from the Notification ($no) object. But outputting a notification is basically just a matter of iterating through the $user->notifications field and outputting them all, or just the ones you want. So in this sense, it actually would be quite easy to utilize on the front-end, but like with anything in PW on the front-end, you have to decide how you want the output to be handled.
Currently it's using the same method as the forum we're typing in (IP.Board). I have not kept up with websockets technology lately, but was under the impression we weren't there yet unless you had specific client-side and server-side libraries to handle it and provide the fallbacks, or were using node.js, etc. I'd gladly implement websockets in the future if they enable us to accomplish the same thing more efficiently, easily and reliably without bloat. Last I researched this, we weren't there yet, at least in our LAMP context. But you likely know more than I do about that technology at this point, so interested in hearing more.