Why is the Employment Allowance not including the Employer National Insurance Contributions of Off-payroll Workers?

As per HMRC Off-payroll working rules, the "deemed employer" / "fee payer" cannot offset the employer NICs calculated on payments to "deemed employees" against the "Employment Allowance".

HMRC Link:-

https://www.gov.uk/guidance/fee-payer-responsibilities-under-the-off-payroll-working-rules