Garnishing someone's tax return is not feasable for the majority of debts. I'm not sure if it's even possible for a federal return, outside student loans and debts to the government. Some states allow you to garnish a state tax return.
You can absolutely be arrested for failure to appear on a civil court case, even small claims. I sued someone afew years back and went back and forth with them multiple times. They were smart enough to show up every time I could have had them held in contempt.
In my jurisdiction, for an average person, you have to sue them and pay filing fees, then appear and get a default judgement, then file to collect your default judgement. If they don't show for that, you can get a "body attachment" and they will have an arrest warrant issued. If they have an interaction with the police, they will be arrested and held, usually until they cough up some percentage of the debt.
This process takes a long time and is difficult for a person to follow through, I ended up settling the debt after 3 or 4 months of court appointments.
Companies with can keep hounding you and if you miss the right court appointment you are SOL.