What is an SLA? It is a Service Level Agreement. It a commitment by the carrier to certain performance levels. Most customers bu into it. Why?
An SLA is NOT a guarantee of repair time or uptime. It is a performance agreement. If you catch the carrier outside the parameters of the terms of the agreement (like the circuit is down, not bouncing), you must get a repair ticket and submit that repair ticket -- numerous times in reality - to get credit.
Ah, the credits. How much is that? Well, on a $900 circuit, that is $30 per day. So if the $900 circuit is down 1 hour, you get to spend days arguing about a fraction of $30. Isn't that productive and revenue generating?
Monitoring isn't much better. It's like buying fabric and paint protection when you buy a new car.