Any Need For AddEventListener() And AttachEvent() At All?

Today I have been testing the event models from Netscape 4.8 and IE 4
to the current crop of browsers. I'd like to write a small event
library similar in purpose to the Yahoo! UI event library but with less
features and code. The Yahoo! event library is one of the best
libraries in YUI but it still seems to me to have some confused
code...that or I'm still confused.

The Yahoo! UI library focuses on using addEventListener and
attachEvent. However, due to the click and dblclick bugs in Safari a
long legacy event workaround is included to use a Netscape4-type event
model for Safari. Something like this

var listeners = [function(event){}, function(event){}];
document.getElementById('blue').onmouseover = function(event) {
for (var i=0; i<listeners.length; i++) {
listeners[i](event);
}
};

With this above example, multiple handler functions can be fired for a
single event. I imagine that this is an old trick that has been around
for a long time, yes?

With all the new browsers I tested with this legacy workaround, the
listener handlers can use event.stopPropogation() or
event.cancelBubble=true and they work as desired. The handler functions
can also use event.preventDefault() and event.returnValue=false and
they too work. These seem to work because the event object passed to
the handlers is a modern event object and not one from Netscape4.

My question is, if Safari needs this legacy workaround, and the legacy
workaround seems to work in all the browsers that have addEventListener
or attachEvent, then why bother with the addEventListener and
attachEvent functions at all? Why not just use the legacy way for all
browsers and all type of events.?