There are a lot of legal reasons why online gambling is legal.
First of all, online casinos are not places where people gamble for real money, instead, they are virtual sites where people get involved in activities in exactly the exact same fashion as traditional tables and slots do. If the activity is free, then so is the law.
This is the reason the majority of online casinos have been operated in the same manner as casinos offline.

With online gambling, however, you do not need to leave your house, as long as you have access to your computer. All you need is a personal computer, an internet connection and a credit card. You may place a simple wager on the slot machines and walk off, or keep playing and winning until you lose all your money.