Usage

Because EV is a capital structure-neutral metric, it is useful when comparing companies with diverse capital structures. Price/earnings ratios, for example, will be significantly more volatile in companies that are highly leveraged.
Stock market investors use EV/EBITDA to compare returns between equivalent companies on a risk-adjusted basis. They can then superimpose their own choice of debt levels. In practice, equity investors may have difficulty accurately assessing EV if they do not have access to the market quotations of the company debt. It is not sufficient to substitute the book value of the debt because a) the market interest rates may have changed, and b) the market's perception of the risk of the loan may have changed since the debt was issued. Remember, the point of EV is to neutralize the different risks, and costs of different capital structures.
Buyers of controlling interests in a business use EV to compare returns between businesses, as above. They also use the EV valuation (or a debt free cash free valuation) to determine how much to pay for the whole entity (not just the equity). They may want to change the capital structure once in control.