Because not all such payments are instantaneous - payable immediately.
It’s agreed that you are not purchasing on credit but you are paying on “credit” terms.
The expense is incurred this month but the due date is not until next month or later.
Electricity/telephone bills which arrive quarterly but paid via monthly instalments.
Annual tax assessment is received but paid via quarterly instalments.
Annual property rates received but paid via monthly/quarterly instalments.
Annual insurance premiums received but paid in monthly instalments.
It could be argued that some of these instalments only need to be taken up when they are actually paid, but that means there is off Balance Sheet liabilities, the accounts would not be of full disclosure.
By placing (highlighting) them in a separate Accounts Payable control account provides an additional management tool to the user in that the Balance Sheet talks to them about payments which are outside the normal suppliers payment cycle.