Why multiple MNS and not just one site encompassing them all?

I see so many people tackling MNS after MNS over and over again.

Since EMD don't have any hue effects anymore, why not just create an authority say... tech blog, instead of making 10 sites about tech products, gaming, etc?

As I understand it, creating an authority site like that would help articles rank better naturally. And in addition, it's the articles that are being ranked anyways so it's not like that is a big deal.

Can anybody offer an explanation as to why my thought process might be mis-guided?

One reason is if you put all your eggs in one basket (authority site), and you rely on mostly SEO traffic, then Google could have an update and your site's rankings plummet even if it's white hat SEO. The more sites you have the better chance you don't go broke on a Panda-like update.

also you can sell the mns site individually.

The EMD still has an effect on ranking, especially when paired with other traffic strategies. The real solution is to do both an umbrella authority site, and separate minisites. Create and map a large 'master' niche site, say on 'shoes' or such, made up of 12-15 popular sub niches. Write 5-10 articles for each sub niche, then manually re-write the articles. One set of articles go to the authority site, the other set to the separate micro niche sites. After a year, you can sell off the MNS, yet still benefit from them through the authority site (or vice versa, sell the authority site, and keep the MNS).

I have been making MNS sites for the last few months and my strategy has been on finding the domains that can be a crossover between the old-style MNS and Authority sites.

Instead of 5 articles and an EMD only, I am adding articles every week or so using LSI keywords as post titles. This gives me a lot more keywords to rank for and also gives my EMD some authority for it's keyword. While not a full-fledged authority site, each MNS has weight and supporting keywords.

True, the days of 5 articles, EMD and a few backlinks might be gone but with a little more organization, work, and perhaps outsourcing, I would go with separate sites for each micro-niche focus.