Most t-shirts made these days are sewn with overlock (also known as serger) and coverstitch machines. They are useful for sewing knits because they sew in ways that allow the cut edge to be finished in a clean way and also to stretch. The stretch part is really important.
But can we talk about how annoying sergers are? I have mixed feelings about using mine, and habitually go to great lengths to avoid it. I have been working on a t-shirt pattern for long-sleeve winter layering tees, and I recently hand-stitched a couple versions of it, instead of using the serger. It was a project which absorbed several hours a day here and there, for a number of days per shirt. Cut the pieces, sew mindlessly, and a few weeks later, a new shirt. The sewing was quite repetitive, which gave me time to consider why I preferred this method, instead of using my sewing machines.
I prefer hand-sewing for the same reason that I prefer to explore a new neighborhood on foot instead of in a car: I get lost more quickly when I'm moving faster, so I don't have to travel as far if I have to turn around and go back. There is a lower risk of crashing. I notice more details and remember it better. Also it just feels nice and travels well, no expensive gear required. So yes, hand-sewing. But who does that now? Only machines make clothes now.
Here are the two shirts that I sewed entirely by hand:
One more reason that I enjoy hand-sewing sometimes more than machine sewing is that I find it easier to control the quality of the seams inside the garment. Better inside seams equate to a more comfortable wearing experience. My second hand-sewn long-sleeve tee is one of the most comfortable shirts I have owned, in no small part because of the smoothness of what I call my "hand-serge".
However, the slow speed of the hand-sewn tee shirt is just not always practical. While I believe in slower fashion to avoid waste, at the same time, sometimes you need a simple shirt without spending two weeks of your free time making it. Stay tuned for the machine-sewn versions of the same shirt.