If you are guilty, I expect you actually don't want to end up in jail no matter the cost. Let us say you face 10 years in jail, you have actually committed the crime: what are the chances you think you will just take it one step further and ruin your family?
Sure. I'm not making a case that bail is perfect, or even good overall, I'm just laying out some of the reasoning behind why it exists.
> Let us say you face 10 years in jail, you have actually committed the crime: what are the chances you think you will just take it one step further and ruin your family?
What are the chances that your friends and family don't understand this, and as such are unwilling to put up collateral as bail? It's not like the the accused get to put up other people's money and property without their say-so. The accused might con them into paying the bail, but really, there's only so much you can do in a case like that. If you could solve that scenario, you could probably eliminate confidence crimes altogether.
In some cases it may remove a significant portion of the money the accused might flee with. In others, it can provide social constraints that are more binding than legal ones. For example, if your parents but their house (or a large portion of what the sale of it would net) up as collateral for your bail, you may be less inclined to flee if it would financially ruin them.