Everyone knows that sports are about money. A person likes to believe in the strengths of the body or somebody else’s body. In any way a people likes to show that this belief is not a mistake and it is worth even the support given.  
In the beginnings of sportbooks this was simply a challenge, but now sportbooks are a huge industry of money. Sportbooks are a strong form of gambling. Back in time sportbooks had a form of man to man fights. This attracted a lot of people and many people made a lot of money with them. 

After a time governments forbid sportbooks. This was not good at all. The games had to go on in private in unknown locations. For the games that were allowed for the public, betting on them was still forbidden. In this way sportbooks became illegal and hard to access. 
If something is hard to reach, people find it even more attractive and more exciting, but sportbooks have severe punishments as consequence. 

Online sportbooks, however, are more popular. There is a simple explanation for this. Online sportbooks are not illegal. Also, modern sportbooks contain a lot of betting possibilities. Simple sportbooks usually are available for local teams or maximum national teams. Online sportbooks cover the whole world. Also they cover a lot of sport types, too. 

Probably there is the shame that stops some people to go to a public location where sportbooks can be made. Using sportbooks online can avoid this situation. Nobody will wee our face when we bet on a team. For example if we bet on the opposite team that our buddies like, nobody will know, except for us.  

Online betting offers us comfort, because we do not have to walk into a public place to do so. We just use our mouse and keyboard and there we are. This freedom and the possibility to remain anonymous attract a lot of people. Probably this is why online sportbooks are more famous. Betting online is easy for everyone. Veterans and starters can use online sportbooks with the same result. With bit knowledge in sports betting online is very easy. 

People became lazy because of the internet and now almost everything is made online. Online gambling has become famous and more people use it than real gambling. Since sportbooks are easier to do online, they became more famous. This will probably stay so for a long time.