There are several reasons as to why you would want to limit the number of fields that Funnel is retrieving:
- Performance - if you have lots of data this can be way to make it possible to import it anyway
- PII (Personally Identifiable Information) - you may want to make sure that sensitive information never leaves your Salesforce installation
- Clarity - a typical Salesforce object contains 200+ fields and this may make it hard to navigate. It is likely that it is only a handful of these that you really need for you analysis
When connecting one of the Salesforce objects the default behavior is to get all fields for the object type. In the connect dialog you can select instead to include the fields you need This will give you a field picker where you can select the fields you need.