Website or server monitoring can additionally be used to verify the quality of hosting services.
Most hosting providers offer an SLA (Service Level Agreements), i.e. a formal guarantee of a particular service level. If the availability level specified in the agreement is not reached, the client is entitled to claim compensation.
It is not hard to guess that it is not in the interest of hosting providers to report real monthly availability and especially if they have difficulty keeping the promised level. The monitoring history is an independent source of information about the real availability and grounds for compensation.