As a result, too many blindly use a sharp needle for embroidery and never know that sometimes, it's the wrong choice. More than likely it's because so many embroidery projects end up being stitched on woven fabrics, and of course then a sharp needle is appropriate...and it's often only after a person embroiders a design on a knit, or stretch fabric, that they notice something 'might be wrong', but even then, not always right away.
So what's lurking on that knit embroidery project that might upset you later? Holes, and possibly even runs. How does this happen? Tiny cuts, caused by the sharp needle as it passes from the top to the bottom of the knit. In fact, a project might even look fantastic for awhile, but as time wears on, it may become evident that a problem exists.
Though this is a very common error, all we have to train ourselves as embroiderers to remember is, that the purposes of needles are the same for sewing AND embroidery, basically a sharp needle is for wovens, and a ballpoint needle is for knits (and of course there are different sizes for different weights of fabric).
It helps to remember by knowing how needles work. Sharps pass through a weave, and while they may still cut a bit, they give a nice clean stitch out that most wovens can take (not all) but knits are different, they require a ballpoint needle that is less likely to cut, and more likely to only pass around the weave, thus less cuts, and less damage (some of which pops up later) when it comes to knit or stretch fabrics.
Nobody whats to put time and effort into a lovely project, only to find out, especially later, that an incorrect needle choice has ultimately ruined the project. Sew be ready, and have some ballpoint needles on hand. You may not need them often, but when you find yourself needing one, you'll smile and think happy thoughts of where you heard this advice!