Personally,
I understand very clearly why they don't have any Model 3s available for test drives;
1) They don't/won't need to until they can reverse the demand to production ratio on the M3. They already have massive orders they cannot keep up with.
2) Those waiting for their M3s have already said they'll buy one without a test drive.
3) Those who have ordered, and are still waiting for their M3,
and who have had the privilege of driving one because their good friend already got theirs...
realize that the M3 is every bit as good as the Model S and X.
In some ways, even better! I've seen many reports of S owners who say they like their new M3 better than their S. And Tesla knows this as well. If they had a Model 3 in their showrooms for the general public to test drive, I have no doubt in my mind that M3 sales would cut into their more expensive S & X sales. This hasn't happened yet because of the virtual unobtainium status that the M3 holds for the foreseeable future.