Posted on VoIP Service Provider explains Why Use SIP Trunks for businesses.
Three Reasons To Use Session Initiation Protocol trunks are as follows:
1. They provide a lower cost per line and lower usage than typical analog lines from the phone company (ILEC or CLEC) or from another provider like the cable company.
2. SIP Trunks provide the end user a lot of flexibility versus traditional lines in

the way of real time routing of calls. Features like Find Me / Follow Me can be updated real time as well.
3. Disaster Recovery is a real benefit. Should the customer premise equipment fail or the power go out, SIP trunks can instantaneously reroute calls to predetermined destinations such as cell phones, branch or remote offices or even home offices.