I think instead of saying that you can "load up anything conductive" or that the tuner makes the transmitter think that the random wire antenna is resonant, it's better to say that the tuner converts the impedance at the end of the random wire to 50 ohms, which is the impedance that the transmitter wants to see.
Having said that, what AB3RY says about random wires is correct. I used a random wire antenna on 80m for a while. The tuner was on a window sill in my shack, and I could run up to 25W before the RF in the shack got to be too much.
The reason to have the tuner in the shack is so that it can be easily adjusted, BUT if you had an automatic antenna tuner and could locate it some distance from the shack, then RF in the shack would not be such a big problem. Several companies make remote antenna tuners that come in weatherproof enclosures.