Most of the times that is enough. But there were always some use cases where you needed four or even five. And of course, just like with all limitations, you can figure out a work around. But wouldn't it be just awesome if APEX offers us more items out of the box.
And in APEX 5 they do! The number of items you can use in a Column Link isn't restricted anymore. So you don't get four. Or five. Or even six. You get "unlimited" (between " because there's probably some 32k sizing limit somewhere.. but you'll get the point).
But wait ... there's more!
The "Target Type" isn't limited to "URL" or "Page in this Application". You can now - declaratively ! - link to Pages in other Applications as well as you can see below.
So one more reason to add to the already long lists of reasons to upgrade to APEX 5 as soon as we can ... maybe general availability will be announced at OOW ??