Why is P&I included in NOI

[Adoney Reid]

Hello BP Community, 

Why is P&I / Debt service included in NOI and not factored into operation expenses when adding up GOI ?

My thoughts are that because;

1. Interest payments can be seen as a return because its a tax deductible.

2. Principal payments are recouped overtime through amortization and depreciation.

Thanks in advance for your input :)