I would say this question is pretty broad and opinion based, but I personally am rather glad that we can exclude
Opportunity records from the
Forecast module. Our business case is we are trying to forecast based on a custom object. So we need a multi-step process:
OpportunityLineItem records which aggregate our order counts into
- Attach these line items to
Opportunity records and assign them to the
Closed forecast category.
- Perform some further manipulations on that data to project what quantity should be in the
- And so on.
If we allow our sales users to throw records into the mix that weren't carefully calculated, that would throw off the entire module. If you don't want to omit any stages, then you have the freedom to do that. If someone else has a different use case and wants to omit all stages available to end users, they can also do that. The solution settled on by the Salesforce team offers maximum flexibility.