Quotas do not roll up in the forecasts tab with Collaborative Forecasting

This is by design in Classic. A manager's quota summing to their team's quota is not enforced. Because Quotas do not roll up, this requires the forecast manager should enter in Quotas per User to determine quotas in excel and then import into salesforce.

When in Lightning Experience, Users can now add quotas directly from the Forecast Manager User and do not need excel to import/update users quota.

Users can directly update Forecast Manager user quota by steps below:  

Lightning Experience : From Setup -> Feature Settings -> Sales -> Forecasts Quotas -> Show Quotas -> Assign Quotas to Users.