I never understood why card counting was frowned upon? I realize they don't like players to have an edge, and they can throw out whoever they want for whatever reason, but I don't understand why they bother with that type of surveillance? Shouldn't a casino instead just use shuffling machines, have limited spread between min/max bets, and not play very deep (e.g 6 of 12 decks) to just nullify any possible counting edge?

I assume it's not illegal to count, even if you are alone and use an obvious tactic such as playing $10 for dozens of hands, and play max bets only near the bottom of the shoe?