It happens if there was a step in the process that includes a DXF file format. DXF is a lowest-common-denominator file format and was created before affordable computers could manage bezier curves. Instead it uses a calculus derived method of approximating curves using multiple small chords or segments - the higher the resolution, the smaller the line segments are to better represent the curve.
Bezier curves are now used because even cheap computers (like commodity PCs) have the processing power needed to calculate the curve mathematics.
But DXF’s attraction is that because Autodesk released the format to public use as an open file format. That got it supported by virtually all CAD programs which of course helped Autodesk dominate the industry 
Virtually every design software supports DXF as an import or export file format. Of course that means it needs to be a simple format so that regardless of the capability or complexity of the software or the computer, it can be used.
Although it’s a 2D format, it’s even found in 3D design programs. Regardless, a complex file design capable software application will create nodes (end points of the small lines or chords that DXF uses to approximate curves) when saving in a DXF format. Then when that file is opened and saved in another more capable format like SVG, it will retain the nodes/chords even though the SVG format can easily support bezier curves.
Now you know more than you ever wanted to about node creation in otherwise smooth looking vector curves 