Yet truly belonging to a community is among the most fundamental of human needs, social beings that we are. And here's the rub: once speared, aboriginal offenders had paid for their crime, and were still fully part of their tribe, with all the requisite privileges and obligations. There were other technical mitigations of the apparent severity of the punishment (eg. the spear head used was specifically designed for the purpose, smooth and covered with antibiotic agents to reduce damage & infection), but more crucially: the punishment was executed within a context that said: "you'll pay for your crime, and it will be a painful price, but you're still one of us".
Employment, for better or worse, is a lynchpin fetish of our current social arrangements, central to full community membership. Denying it is tantamount to community expulsion: a truly savage punishment.