"Xfig is an older package, developed for Unix workstation environments such as SPARC. If you were using such a system to prepare research papers in the 1990s, it’s very likely you would have encountered it. The output from Xfig was very easy to incorporate into TeX or LaTeX papers, and this made it a favorite program among academics.
"Of course, it was not very competitive against proprietary software then available, such as Corel Draw, but those programs were generally not available for Unix, and neither were they really designed for the technical drawing needs of academic publishing. So, it's not surprising that Xfig is weak on such finer artistic tools such as Bezier curve editing. Instead, Xfig has simpler "interpolated" and "approximated" "spline curve" tools and a separate "polyline" tool (a spline is slightly simpler than a Bezier curve and therefore not quite as flexible to edit). This approach may not be as intuitive for editing general curve objects (the workhorse tool for creative graphics in programs like Inkscape), but it works very well for simple line-art illustrations."
