I'm not a lawyer, but this is my understanding (I'm in the USA):
On bail - suspects are presumed innocent until proven guilty. The idea is that someone accused of a crime can free themselves until trial, with the bond money used as an incentive to get them to return to face trial. Well, there's also the incentive that they will be hunted down by bounty hunters if they flee.
This has two benefits. The accused can mount their best defense, fee from the confines of jail. The other, which is probably most important, is that the government can't just jail someone for a long period by accusing them of a crime.
The use of money for bond is imperfect, but it seems to work. Bail is set with the amount varying with the severity of the crime. Severe crimes (such as murder) can be refused bond, forcing the accused to stay locked up.
For those who lack the means to post the full bond, there are people who sell bail bonds -- in other words, they will post the full bail, if you pay them a percentage and a fee. The understanding is that you show up for court, or they will use civil suits and bounty hunters to get the money from you and put you in front of a judge forcibly should you flee.
The "accepting money to mould policy" part? Wow. Our lobbying system in general in the US is a mess. I honestly have no defense for it. If I was in charge, I'd place much stricter limits on lobbyists.
This isn't just about a person who misses a court date because they're lazy; it's also about people who may flee to a different country, or start working under an assumed name, or anything of the sort.
If they've already paid, they have some incentive to come back and be able to reclaim their bail money.
If they do skip town, sending cops after them to track them down and arrest them again is expensive. That's where the bounty hunter part comes in; if they skip their court date, their own bail money is used as incentive to encourage police officers, sheriffs, or private investigators to capture them.
In many cases, this isn't the romantic image of a western cowboy hunting down dangerous criminals in caves, but just the equivalent of a debt-collection agency, that calls them, mails them, files information with credit agencies preventing them from receiving credit, and so on.
Fair enough about tracking down people who flee. Wouldn't that be some evidence towards a conviction though?
There's one thought that applies to smaller population. If someone disappears you can just stop worrying about them? Hiding from public and going to jail has close to the same net benefit for society. Just thinking.
Also slightly related - why is it acceptable to persuade a court to release suspects by simply paying them bail money in England and America?
Money walks all over morals.