xeyes purely for fun? What is the point of having it installed by default in many linux distrubutions (in X)?
xeyes is not for fun, at least not only. The purpose of this program is to let you follow the mouse pointer which is sometimes hard to see. It is very useful on multi-headed computers, where monitors are separated by some distance, and if someone (say teacher at school) wants to present something on the screen, the others on their monitors can easily follow the mouse with
xeyes is not only fun it is a useful utility if you have a big screen and a small cursor. Second, it is an example program for the x toolkit intrinsics (Xt) library. XEyes implements an Xt Widget (Eyes.c) and has a nice, clean xt initialisation sequence (xeyes.c). It also initialises the "application icon" (XtNiconPixmap) and catches the window quit event from the window manager (WM_DELETE_WINDOW). A very useful example.
For multiple large displays, 2 Xeyes work better: Assuming you have two big moinitors side by side, place them on the top right corner of each monitor. You mouse locates at the intersection of the two sight lines. That's exactly my current use case.
Although, yes, two eyes (one xeyes) creates two sight lines, but the angle is too small for big monitors: the two sight lines look very much like one. Four eyes (two xeyes) work better.