Google's testing must have shown them that removing the ads on the sidebar will ultimately make them more money.
(source: Google's AdWords account team)
If you are a small business or one person the main block is simply overpriced - by a long way for many keywords, and is just the brands usually.
Top 1 or 2 in the sidebar are usually noticeably cheaper and do bring in a decent amount of clicks for popular keywords. I'd call it the sweet spot for someone bootstrapping or a tiny business. Sure you'll get more clicks bumping to 3rd in the main block, but only if you can afford 24/7 coverage on that keyword. If your budget is limiting display then increasing bid will mean less business overall.