That financial barrier is a problem in those other fields too, and it does disproportionately affect people from disadvantaged backgrounds in those fields. Your argument is basically "well it's tough for the poors to become a doctor, so it would be okay if it's tough for them to become a software engineer too!"
EDIT: also, the costs incurred by becoming a doctor or nurse are debts to educational institutions and licensing boards which, ostensibly, are doing good by educating and regulating. This is a proposal for a financial barrier imposed by your employer, and paid for by your social or professional networks. It's not the same.