True, even with a simple strategy you can cut your theoretical loss to about 1-2% (without counting cards). But casinos have blackjack because most players don't know how to play. Most people don't follow that simple strategy (they often have leaflets explaining it too!).
With counting cards you can make it profitable for you. But casinos will make life very difficult for you if they find out you're counting cards. See also the movie about the MIT Blackjack team: http://en.wikipedia.org/wiki/21_(2008_film)
This signaled to me that the casinos -- or at least the one I worked at -- in general treat the overall risk of blackjack as the low risk that skilled (non-counting) players can achieve, regardless of the number of people that might come in and ignore the simple, effective strategies to the game. Personally I think that the casinos would rather reduce the risk to themselves from skilled players as well as card counters and just remove all the blackjack tables, sending all those inexperienced gamblers onto games like roulette where they might lose a larger portion of the money they brought with them.
True, but ... isn't that the case with every game in the casino?
Once upon a time, actually, blackjack wasn't terribly popular; craps was the king of casino games. But after Thorp demonstrated it was beatable there was a surge in demand for blackjack. Turns out, nearly all those new blackjack players weren't really very good at counting and lost money hand over fist. Thorp's work (among others) led to increased casino profits and lent an air of legitimacy to gambling; it wasn't just luck anymore, if you "worked" at it you could profit. [Citation needed].
[Thinking about slots, reminded me that in my previous comment I was talking about table games when I was talking about roulette being the worst odds. I don't know if that's true. I haven't crunched the numbers, but that's what I remember being told as an employee.]
You probably can't 'win big' with such a strategy, but you've at least minimized the probability of a loss from 50% to 25%. You've also minimized the probability of a win by as much too, though. I'm no stats guru so I don't know how well this would work out on an actual roulette table...
{edit} I should mention that I worked at a casino for a while, and roulette is the game with the highest probability in favor of the house. Blackjack is the lowest. Casinos really only have Blackjack tables because patrons want them, or else they would probably get rid of them pretty quickly. {/edit}