1. Redundancy - although failures are rare, they do occur. So if one provider has a problem, traffic to all other points is not interrupted.
2. Pricing - you buy from multiple providers and thus are not locked in.
3. Latency - your customers want the lowest latency.
3a. Often times, companies will run an application in the data center and have remote offices connect over a VPN to the servers. Those remote offices will be in different geographic areas and will be using different local providers, all of which will have different network paths to reach you.
Peering - if you are large enough to provide say 100Mb/s or more of traffic continuously to one provider's network, they may choose to peer with you at little or no cost. This means that they give you the connection because the traffic is going to them directly and they don't have to maintain other high speed connections to some third party that they may have to pay. There is a lot of negotiation and at least 3 separate pricing strategies that each side can follow.
The simplest is "bill and keep" which is that each side provides no-cost access to the other's network, and they each bill their own customers and keep the proceeds.
2. Pricing - you buy from multiple providers and thus are not locked in.
3. Latency - your customers want the lowest latency.
3a. Often times, companies will run an application in the data center and have remote offices connect over a VPN to the servers. Those remote offices will be in different geographic areas and will be using different local providers, all of which will have different network paths to reach you.
Peering - if you are large enough to provide say 100Mb/s or more of traffic continuously to one provider's network, they may choose to peer with you at little or no cost. This means that they give you the connection because the traffic is going to them directly and they don't have to maintain other high speed connections to some third party that they may have to pay. There is a lot of negotiation and at least 3 separate pricing strategies that each side can follow.
The simplest is "bill and keep" which is that each side provides no-cost access to the other's network, and they each bill their own customers and keep the proceeds.