Is Blackjack beatable?

Yes. You can beat pretty much any blackjack game and here is why...

1. The most important thing is that there is a spread, so you can bet different amounts each hand. Combine that with card counting and some betting strategy and you can bet more on hands that are in your favour and less in spots where the odds are against you.
2. Even without counting cards you can reduce the house edge to a minimum, if you use some basic strategy. In most casinos that will actually give you a win through their loyalty programs.

Why don't more people do it then?

Well it's not as easy as it looks. To beat a blackjack game you have to count cards, memorize the betting strategy chart and also look like you are not doing either. Even dough it's no illegal it will still get you kicked out of casino, if the pitboss notices you doing it.

Another big problem that a lot of people without a background in math/probabilities have is also realizeing that it's a long term game. Like all gambeling games it's based on probabilities of something happening and nothing is a 100%, except death and taxes :). In fact in blackjack edges either way are pretty small, so you have to play a lot to get your actual long term resoults. This means there will be a lot of positive and negative monetary swings along the way and people usually have a hard time dealing with that.

Blackjack is fun!

Not everything in life is about money. Even for those that don't feel like learning charts and card counting, blackjack can have different value. It's really fun! In my opinion it's one of the most fun casino games, especially when you get some friends around to cheer you on and some free drinks on the house :)