Aren't the yanks nice?
They let people chill for a bit before they have to voluntarily turn up at the joint and start their sentence. Here (in Aussie) you get sentenced and they take you from the court down to the van in the basement which takes you straight there. Too bad if you have affairs such as a house/family etc to deal with. Granted you might know it's coming before the actual sentencing, but once the sentence is passed, or if bail is revoked sooner, you're gone. None of this "I have to sign into the clink in a few weeks, gives me time get my shit sorted, possibly including a one way ticket to Antiextraditionistan".
I know this isnt blanket, but I know myself a few people who have had to get locked up in USA for minor offences (drink driving etc) and they were allowed to make their own way there pretty much as they saw fit. I'm guessing violent crimes wouldn't get this luxury.