Why doesn't the Schedule I for Form 1041 generate on every return?
Schedule I (1041_I) Alternative Minimum Tax – Estates and Trusts is the 1041 equivalent of Form 6251. Like Form 6251, Schedule I is governed by the option Print Form 6251 only when required (Setup > Options > Form & Schedule Options tab). If a Schedule I is required, this option will not affect it. If the Schedule I is optional, checking the box will suppress the form. You can choose to force the form to print by going to the PRNT screen inside 1041 data entry and checking the box Produce Form 1041-I (Schedule I - AMT) at the top left.
See the Instructions for more information.