Petition job grants

Job grants are paid to people returning to work after being on benefit for 26 weeks.£100 is paid to a single claimant and £250 paid to a claimant with family.The grant is paid if the job is expected to last 5 weeks or more.It is paid when the claim closes and no proof is requested that the job is likely to last longer than 5 weeks.Lots of claimants return to claiming benefit before 5 weeks work has been undertaken.Why is the grant not paid 5 weeks after the new job starts?This could easily be programmed in to the computer system and would save a vast amount of money.