The main reason that I love to play online is that it is a lot more convenient than having to actually go to a casino. Like most Americans I live in an area where there is a casino located nearby but it is hardly in a convenient location. Rather than spend an hour driving to the casino I can just turn on my computer and play whenever I want. Not only can I play when it is convenient for me I can also play for only short times if that is what I want to do. If I am going to drive to the casino I am not going to just play for half an hour and then come home, I am going to spend several hours there. Obviously I don't often have that kind of time. Playing online makes this a non-issue.
I also like to play online because there are no crowds around when I do. Certainly there are times when the excitement of being at the casino around all of those other people can add to the fun. Of course when you have to wait for a seat at the table the crowd isn't so great anymore. There is also the people at the casino or the local cardroom who aren't so much fun to be around, everybody is fun when they are winning, this really isn't the case when they start losing. When you play at online casinos it really doesn't matter what the other people are doing since they aren't there.
A related benefit of playing online is that if find it easier to concentrate on what I'm doing. There are a lot of games at the casino that really require you to pay attention to what is going on in order to execute the best strategy. This can be a problem in a crowded casino. With all of the noise and all of the other distractions that exist in a casino it really can be hard to pay attention. Again this is not an issue if you are playing online.
Playing online also allows me to change games very easily, another advantage. When you are playing at regular casino if you want to switch games you have to collect your chips and then walk around to find a seat at the game that you want to play. This can be a hassle which is why most people will just remain in their seats and play the same game. When you are playing online this is less of a problem since you can change games pretty much with a click of a mouse. If you want to play a few hands of blackjack and then switch over to roulette for a while you can do just that without a problem. Having the variety in the games that you play can really make them more fun.