Why do so many manufacturers include a DI in their preamp pedals (without the option of one that does not have it)? I am thinking about these popular choices: Sadowsky Preamp DI, SansAmp Bass Driver DI, MXR M80 Bass DI +, MXR M81 Bass Preamp, Mesa Subway Bass DI Preamp. I am sure there are many more. For live sound most, if not all, amp heads have decent built in DI's or either the player and/or the venue has their own DI. It seems like an added cost for a (potentially) unused feature. With the exception of the Tech 21 VT Bass, I am not aware of a manufacturer that makes a DI and non DI version. What say you?