At the risk of impuning your instructors’ street cred, a couple of points: There is simply no reason (in a Citabria or Decathlon) to either hold the stick back when taxiing or force the tail up prematurely during the takeoff. During the taxi all you’re doing is prematurely wearing out the tailwheel. With two people in the airplane, there is probably 250lbs of weight on that corner of the fuselage, hell, I defy you to try to even lift the tail, (try to do that sometime) so what’s the point of back stick? How can you tell when the tailwheel is wornout? It shimmys! I tell my students to be gentle to the tailwheel, it takes a great deal of abuse. I’ve seen broken u-bolts holding the leaf-springs on more than one occasion.To be fair, there may be some airplanes that are very light in the tail (or heavy on the nose) in which stick back can’t hurt, but in such airplanes the real issue is to be light on the brakes. As tailwheel airplanes go, the type you’re learning in is the EASIEST, which is to say, in some tailwheel airplanes, agressively raising the tail early in the roll will result in an uncontrollable veer to the runway lights; perhaps you’ve heard the term “exit, stage left.” Can you do that? Sure. But it makes little difference unless in a strong crosswind, other than improving your instructors’ view. I taught in Citabrias for over 1000hrs.
Okay, I'll bite... the Citabria and Decathlon were the main airplanes I taught tailwheel flying in. But it's been awhile. Nowadays the only tailwheel airplane I fly somewhat regularly is a J-3.
The trick with all of these discussions is that any advice we tend to give as instructors can never been absolutely true all of the time. There are always exceptions.
In general, I recommend the old "climb into the wind, dive away from the wind" advice which appears everywhere, including FAA publications. But I make it a point to say "relative wind." If you're creeping along with a 15 knot tailwind gusting to 20, sure, hold the tail down with forward stick. Like you mentioned, with two aboard, the tail is pretty well stuck on the ground and it would take a hefty pull for a person standing by the tail to get the empennage off the ground. But as soon as there's relative wind, it's an airfoil and subject to doing what airfoils do.
I tend to think of things from a Human Factors standpoint so I think about the possibility of students modeling my behavior across the board without consideration for changing factors. Let's say you have a lightweight pilot, maybe 120 lbs., flying solo which of course is in the front seat in a Citabria or Decathlon. The tail of the same airplane will come off the ground easily. Because we as instructors tend to fly the same airplane a lot it is very easy for us to build small modifications into our behaviors based on the changing conditions, i.e. "don't wear the tailwheel out with aft stick while taxiing at normal speeds in calm winds with two persons aboard." But those are two many modifying factors for most people new to tailwheel flying to consider. I.e. it's probably better to let them give the tailwheel a little extra wear and tear rather than the possibility of the wrong input at the wrong time.
Greg brings up a good point, taxiing on a rough surface, for example, with a bit of wind -- you're going to want that stick back to keep the prop clear as you roll over the uneven surface.
Further, especially when instructing in tailwheel airplanes, I believe it's an instructor responsibility to remember that while a Cessna 172 and Piper Archer are only nominally different and can basically be flown with the same techniques, the same is not true of two different tailwheel airplanes. The ground handling characteristics of two "benign" tailwheel airplanes can be dramatically different. Taxi around in a Cub with any kind of wind while failing to consider the position of the stick, and there can be consequences for the unwary.
I agree regarding premature lifting of the tail on the takeoff roll. I call the range of airspeed from brake release to "tail up" speed to be "no man's land." The tail should either be planted on the ground or flying. Wait for the correct airspeed (no need to use the ASI -- it can be eyeballed/felt) and then decisively -- but
smoothly -- bring the tail off the ground. Leaving the stick loosey-goosey in the middle of the square is the least desirable option yet it can and does work fine for many airplanes, i.e. "fly it off just like that..." but again, considering it's a training operation, the stick ought to be brought forward at the proper time on the takeoff roll to teach good habits. Later on in the tailwheel flying journey the pilot can decide how he or she wants to fly the particular tailwheel airplane they're enamored with.