Hm, I think that this is my longest entry title ever. Never had before. Then, I ask again. Why is it that most Magicians use card tricks in their act? It is because the performer start entertain people with gambling? The answer is MAYBE!
Card tricks is a must tricks that should be perform by magician when they performed. It is essential part of any Magician’s performance.
I think, the most reason why is because the magic card tricks is most magician's first trick. They learn their first magic tricks using card.
Magic card tricks have different level of difficulty from easy/beginner to advance/intermediate to expert. Some of simple but still give a lot of impact tricks are very easy to learn. Some are automatics magic card tricks which is mean no need to much practice, some are need to prearrange the deck, and some are need to know the cue card.
For advance magic card trick, some are need a little practice, but some need a lot of practice. Some of the magic card tricks are need a little sleight of hand. The example is, the magician make the chosen/signed card jump from the middle of deck to the top of the deck.
In expert magic card tricks, there are a lot of practise need to be done before the magic card tricks can be perform. It's contains hard sleight of hand, misdirection, hign confidence level as well as good patters. The quite good examples is, to make the card disappear from the deck, then jump to inside the shoes.
Some of magic card tricks will be perform with some kind of skills to make the magic card tricks looks beautiful and professional called "flourish". To perform flourish, the performers need to practice it a lot and to make the florish come as second nature to himself.
The other reason why most magician use card tricks in their performance is because the card/deck itself is easy to carry. You can put it inside your pocket and can be perform anywhere, anytime either being ask to perform or you want to perform to attract crowd.
The last but not least, it is cheap to buy your own regular and normal deck and start to learn your first magic card tricks.