The Contour (Spatial Analyst) tool allows the creation of overlapping polygons (via the Countour type parameter using "CONTOUR_SHELL_UP" or "CONTOUR_SHELL") but it does not allow for irregularly spaced output. When using contours outside of the classical usage (isolines for equal elevation) but instead for instance to depict regions of constant temperature (e.g. -10, -5, -2, 0, 2, 5, 10, 15 °C) in a climate map, the intervals are not always constant.
Adobe Illustrator does not allow editing that maintains topology of shared edges (which would be the case if one used the GDAL contour utility in QGIS, which allows for irregularly spaced countour polygons, but does not produce overlapping polygons, only adjacent ones with shared edges) and the topology maintaining editing of adjacent polygons in QGIS and in ArcGIS Pro can be very tideous. The possibility of an overlap makes it therefore easier for subsequent cartographic editing (in Illustrator as well as in a GIS interface), as polygons can be freely moved without creating gaps.
@BobBooth1 has presented a workaround in my post Produce overlapping contour polygons with irregular intervals in ArcGIS Pro? but it would be a great addition if the Contour (Spatial Analyst) tool would allow for the input of multiple break points instead of one single interval starting at a base contour (the base contour would then be redundant).
