This is certainly an age-old bone of contention! I have never seriously practiced full-spread divination for myself as a matter of principle, since the potential for subjective bias/"blind spot" can unintentionally skew the interpretation and not produce an optimum outcome/action(inaction). Not saying this WILL happen, but unconscious imperatives can be slippery at best and we often fool ourselves. Early on, I used to practice spreads to get a feel for the process flow and exercise my "synthesis and integration" (thanks again for that, poopsie!). But I may not be a good current example since I've had a "willing victim" (aka "wife") for the past 30+ years who encourages me to read for her frequently (did someone say "tarot vending machine"?)
I do think the practice of single-card draws can have merit if kept in perspective. Much like the use of daily astrological transits, I can see how a random draw can be read to reveal the likely tone or "tenor" of the upcoming day, especially if the planetary/zodiacal rulerships of the card reinforce an ongoing transit. For example, if I were going into my workshop to use a power saw with a "hard" transit of Mars going on and pulled up The Tower or one of the lower-emanation (in Tree of Life terms) Swords (9 or 10), I might take more than my usual care to focus on the work at hand and not let my attention stray. I wouldn't let it dictate whether I start the job, although a 3-card progression might show a tendency to become sloppy or unfocused in the middle of it, in which case I would be watchful and take a break before something happens. My point is, if you seize upon the "flavor-of-the-day" and watch for its signature in the small things as well as the large, you may unearth unforeseen opportunities or avoid pitfalls. Even if nothing untoward occurs, you can at least feel that you were informed and ready. If the cards truly sync with the unconscious mind through the act of shuffling and random selection, I see no reason why the practice can't be instructive, if only in a non-material way. Just sayin' . . .
