Via advantage play, you're overcoming the house edge vias your bet selection. For example, sort players at bac. and blackjack. They're no longer playing just the random game, but are using information about the cards in order to place a bet that will have an edge.
Why play when there's a house edge?You might wonder, "Why play at all if the house has the advantage?" That's a good question. You're likely to lose when you gamble, which is indeed an excellent argument for not gambling.But of course, even if the odds are against you, it's possible to win. That would have to be the case, otherwise nobody would play. Anything can happen in the short term. The odds are against your getting heads twice in a row from two coin flips, but it could happen. If you played baccarat for a year, you'd expect to be seriously in the red at the end of that year. But what about for just a weekend trip to Vegas? You could certainly come out ahead. The odds are against it, but it's definitely possible.
Another reason is that if you know what you're doing, it's cheap entertainment. A blackjack player using at a $5 table expects to lose only $1.50/hr. If she tips $5/hr. that's a total loss of $6.50/hr. That's cheaper than most forms of entertainment, like movies, and it's certainly cheaper than Vegas shows.