4.1The Salesforce Connector's job

Without a connector, you would have to write something conceptually like:

obtain OAuth token
        ↓
construct Salesforce URL
        ↓
set Authorization headers
        ↓
serialize request
        ↓
send HTTPS request
        ↓
handle status codes
        ↓
parse Salesforce response
        ↓
refresh token
        ↓
retry connection failures

With Mule:

Salesforce Connector
        ↓
Query / Upsert / Update / etc.

So instead of treating Salesforce as an arbitrary HTTP endpoint, Mule gives you Salesforce-specific operations.

That's why I would normally start with the connector rather than manually calling Salesforce REST endpoints.