So if you were making the laws, the trooper that pulled over Timothy McVeigh would have just given him a summons and told him to show up in court?
I agree that holding someone without a conviction looks like a violation of the presumption of innocence. This is why the right to a speedy trial is in the constitution, to minimize this violation. Unfortunately that right is somewhat theoretical. Depending on the crime, people spend on average between 50 and 200 days in jail before trial. This is way too long and we should really figure out how to streamline these processes for the cases where someone really does need to be held for trial.
Well, it's certainly not a real concern that is addressed by cash bail; if someone is inclined to flee prosecution for a major crime, a cash bail will either (a) be unaffordable, and thus equivalent to no bail, or (b) affordable and an acceptable cost to sacrifice when fleeing.
If you think about what people are fleeing if they are fleeing bail, it makes sense. Bail is essentially taking money. If someone can post a million dollars bail, but thinks they can evade the Justice system by fleeing, a million dollars probably isn't going to be worth a sizable risk of being imprisoned for whatever the potential sentence is for their crime.
OTOH, non-cash-bail systems tend to put more focus on monitoring and related conditions which have a real and meaningful impact on flight.