Don't Salesforce provide support? Yes. And No.
For anything that's platform specific then your best bet are the excellent support teams. Just log a case and you're in safe hands.
For custom builds and processes then a partner with intimate knowledge of your business and your org can get issues resolved quickly and efficiently. Maybe even discover issues with the quarterly updates BEFORE your production org is automatically updated.
"Every business is dynamic." Therefore it can be difficult to adjust automation functions, sharing and delegated responsibilities across teams as structures change. We can review, define and manage these change processes to assist these transitions.
Salesforce update the platform thrice yearly; as part of this process it is recommended to review any custom functionality to the latest upcoming versions to catch any issues before production is updated.
Data storage running out? Too many rollup summaries? Snapshots getting out of control? Reports out of date?
Managed support can keep an eye on any impending issues and resolve before any downtime is experienced.
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