Maybe scary is the wrong word to use to describe stick insects. They are pretty peaceable insects and don't really bother people. However, some people are put off by their ability to camouflage themselves so well. There is something disconcerting about realizing that what you thought was a dead branch was actually a bug that just walked away.
Even more disturbing to some is the sheer size of some stick insects. The longest have bodies that are 12 inches long. Some of the more common stick insects kept as pets are significantly smaller than this, but as far as bugs go they are still really big. The body of the stick insect above (I believe it is a Vietnamese stick insect) was about 3-4 inches long.
Stick insects vary in how easy they are to care for as pets. Because they are considered a possible plant pest (agricultural pest) it may be illegal to keep stick insects or import non-native stick insects where you live, and you should never release them into the wild.
- More about Stick Insects as Pets