Most people don't have enough cash on hand to pay any amount of bail that would serve as an incentive for them to get back--especially not most people who get arrested on criminal complaints.
The bail bondsman actually provides another service to the court: he has the legal power and financial incentive to apprehend a suspect and return them to the custody of the court if you skip bail. In other words, instead of the county sheriff having to worry about apprehending everyone who skips bail, they effectively outsource it to the bail bondsman. The bail bondsman thus has an incentive to make sure you don't skip bail, or failing that, to make sure that he can apprehend you--and these risks are priced into the effective rate of interest on the bail bond. (Most "bounty hunters" in the US are just bail bondsmen trying to recover their suspect, or somebody working for or contracted by the same.)
It's a fairly underrated and underappreciated market mechanism where the entire problem of "making sure people show up to court if they are on trial" can be handled by a competitive market, usually more efficiently or humanely than most local governments would do themselves. But it involves money changing hands, which gets certain people all up in a lather about abolishing it.