Why people do blogging?

you answered your all questions yourself.

Lets have a go at this...

because most of humanity is under the false pretense that other people actually give a fuck what they think so they write it down.

i use my blogs to promote my single page sites i make for the most part.

Some people make money at it. While others are just lame and have nothing better to do with there lives than to post everything about their day online for all to see.

yes keywords are an inherent part of blogging... blogs get into the SE's because of that, and the fact that most blogs are be default set to auto-'ping' the search engines upon update...

se's list you not only for pertinent keywords, but for frequency of update, quality, linking criteria such as 1 way links, overall links etc.

etc etc etc

WTF are you talking about!?

killbloggers.com

Read up!

you don't need keywords on your site to rank high for these keywords. people blog because everybody blogs and they think it's the way to get se traffic.

pls tell me you're joking and im just not catching it

blogs = money in the bank

I blog because my car wouldnt start this morning...

Sorry... Typo... Should read:

I do blog because my car wouldnt start this morning...

A blog CMS is easy to manage and update. Install, choose template, install plugins, set and go. Since post titles are used as page titles and blogs have (or should have) text, you got some nice fodder for the spiders, many subpages, a good linking structure. Basically an easy and comfortable way to build a good looking SE friendly site. That's what made them popular, every newb who thinks photoshop is some store in town and knows shit about html and php can build one without mayor problems.

Frequent updates help to attract the spiders, make them crawl more often, although they are overrated ranking wise...I have sites on #1 for 1m+ exact match terms that were last updated in 2006.

There is nothing magic with them, they don't have a built in ranking advantage, a hand built site isn't worse, but more work.

One of the main advantages is that you can use them for automated link generation, too. Building a splog network giving you thousands of (low quality) links is a matter of a few hours. WP MU with autoblog plugin, a good feed rewriter (not one of those crappy "replace pussy with cunt" ones), a dozen domains and IPs, auto social bookmarker and pinging tool, done.

You can do some more evil stuff with them as well, auto link generation via syndicated (excerpt) feeds and auto trackbacks, etc.

As for the one-page-wonders you mentioned: They work very well, too, but you often waste the opportunity to rank for long tail keys related to your main key with them.

Basically because they are sheep and follow other blind sheep in an endless journey for the end of a circular road.

because blogs are very easy to manage - integrate content and so on