Let's imagine we have a single mother who got knocked up by two or three different dead beat dads, none of whom pay child support because they are either unemployed, in jail, or dirtbags who hide from the law. She's not exactly a great decision-maker and lacks education and job skills, so she won't be able to find anything more than a minimum wage job.
This person doesn't have the time to work 8 hours of community service, and if she did (let's say she doesn't work at all) she couldn't afford the daycare costs.
Ultimately, the question becomes, are you willing to let her children die because their parents make bad decisions? Alternatively, do you want to pay enormous legal fees to take custody away from her and put her children in the costly foster care system? As a final alternative, would you prefer to spend tons of money to investigate each claim on a case-by-case basis so we can determine when a person actually can't do the community service hours, including follow-up investigations to determine whether circumstances change (maybe a dad gets out of prison, gets a job, and starts ponying up support for daycare), just so we can get some labor out of someone who may not be a very productive worker anyway?