Why does Cash-on-cash (CCR) not take into account tax benefits?

[Vik C.]

This has puzzled me quite a bit. 

Particularly when looking at real estate as an asset to invest in vs. alternative investments (equities, bonds, commodities, etc.), it seems silly to me to ignore total returns. Total real estate ROI should include 1) cash flow, 2) tax benefits realized each tax season in the form of real cash (non-operating items such as depreciation, mortgage interest, RE tax), 3) equity. Now, I can understand why some folks might want to leave #3 off the table since it is accounting money and not cold hard cash, but I do not fully understand why people do not include the tax benefits in cash on cash. I suppose one reason is that everyone has a different tax rate so it doesn't make sense as an objective metric that can be used across various investors. But for calculating real estate attractiveness, this absolutely needs to be part of the calc.

From doing the math, a recent model I ran showed a CCR of 7% but a CCR (incl. tax benefits) return of 17%. Not even taking into account equity. This is a huge difference and makes all the difference when comparing RE as an asset class to equities.

Am I stating the obvious or is this often not considered in public discourse on the returns on RE investment properties?