There are certain traditions that you have to obey in whatever you're doing. In friendly competitions, it's customary to shake hands after playing to show that there are no hard feelings, or at least to give you the chance to try to crush your opponent's hand if you were beaten especially badly. At Christmas, it's traditional to struggle to compose your face into something approximating gratitude when opening a package which contains some "hilarious" socks that are in fact too small for you to wear anyway. When decorating, the tradition is that you only notice that you've missed a spot once you've packed away all your brushes and when leaving a job it's traditional to pretend that you actually like the deadbeats you've been saddled with every day for the last few years and you aren't utterly thrilled at the prospect of moving on (and inevitably saddling yourself with a remarkably similar set of deadbeats).
Blog writing is no exception and has its own tradition - the "I'm sorry I haven't posted in ages" post.
The "I'm sorry I haven't posted in ages" post, or ISIHPIAP as it's known by literally no one at all, serves three important functions. The first is to assure the blogger's hordes of loyal readers (in most cases, the same people that refer to these posts as ISIHPIAPs) that the blogger hasn't been abducted by aliens, shut down by the FBI/CIA/MI5/RAC/YMCA for telling THE TRUTH, infected with a horrific tropical disease, or found by the authorities, having been partially eaten by their own cats, after neighbours started to complain that the smell was even worse than usual. The ISIHPIAP is proof of life, of a sort, and allays any fears that may exist in the blogosphere about the blogger's wellbeing.
The second function of the ISIHPIAP is to ease the blogger back into things. As with any task, blogging is easier with practice, and as he or she spends more time in the real world (scavenging from bins, avoiding eye contact with other humans, hissing at sunlight, that sort of thing) the blogger will find that the mental muscles to create the scathing yet somehow subtly beautiful prose that is their medium begin to atrophy. The ISIHPIAP allows the blogger to discuss (at length if they are especially vain) something that affects them deeply and which they are intimately familiar with, namely themselves and whatever pointless waste of time they've been indulging in instead of the crucial work of typing barely literate hogwash into a browser window.
The third function of the ISIHPIAP is perhaps the most important - it helps to soothe the blogger's ego. Like all areas of human activity, blogging has a series of numbers associated with it, which an insecure person (for example, the sort of person that feels the need to keep a blog) can easily be tempted to use as a score card. If their "friends" have more followers, more views, and indeed more posts on their own blogs, the blogger is bound to feel that they are losing at blogging, much in the same way that they used to come last in school sports days. The sting of this realisation can be harsh, and so the blogger feels it necessary to get something, anything onto their blog to redress the balance a little, and make at least one of the little numbers on the dashboard go up.The ISIHPIAP reminds the blogger of the thrill of making the little numbers go up, and asuages some of his guilt at letting his loyal followers (see: people that call them ISIHPIAPs) go without the benefit of his boundless wisdom.
In the end though, the ISIHPIAP is a tradition, and that's why it's done - they are written because it's the done thing and always has been. Wherever there are deeply lazy and untalented people with blogs, these posts will have a place.
I'm sorry I haven't posted in ages.