Large companies sometimes don't actually 'do' any of their own IT work. There are layers of SLA's across data centers and applications, spread across multiple vendors, contractors, etc.

Everything must have a legal contract that specifies support terms, penalties, etc. Large company's motives are risk avoidance to ensure profits for shareholders.

Basically companies will pay a premium to have someone they can call and yell at if something goes sideways. Usually corporate finance departments have no logistical way to accept a reimbursement from a vendor for missing a SLA but they like to put clauses like that in a contract.

The other part is the professional services arm tied to the sales process. RH can provide experts that only they can provide - they are the ones writing the code sometimes. Other companies like Oracle have professional services but I doubt they are committers on the products being sold.