While bulky yarns are great for learning how to see your stitches, that is a double edged sword in and of itself. If you could see your mistakes in these yarns when you first learned to knit, so can everyone else now. Moreover, if every stitch or two makes up a whole inch, it quickly becomes very important that you make no mistakes in your shaping. On a size 19 (15mm) needle, being off by one stitch on one shoulder will be noticeable in the finished product.
Ultimately, variety is a good thing. Knitting involves very repetitive movements in the hands, wrists, and arms. In the post-industrial work environment, most of us have enough of that just from work, so its really important for knitters to keep their habits healthy to avoid injury. More so than smaller needles, big needles require a lot of movement to manipulate successfully, just because of their size. If you don’t believe me, write something with a standard Bic pen and then switch to a jumbo sized permanent marker. It takes a lot more effort to achieve a similar degree of control.
In all fairness, it’s good for knitters who prefer smaller gauges to work on large ones from time to time. I know that when I spend a lot of time on smaller needles, I tend to concentrate all of my movement into my hands and away from my wrists and arms. Using a large needle reminds me and retrains me to make knitting closer to a whole body experience.
If you learned to knit on large needles and always felt a little intimidated by needles smaller than an 11 or 13 (7 and 9 mm respectively), it’s great if you are learning new techniques and have found a way to do so on familiar territory. But let me encourage you, if you want longer lasting more forgiving garments, to experiment with a slightly smaller gauge from time to time. You may very well impress yourself.