Anytime I see wirenuts or devices taped, my first thought is either 'hack' or 'amature'. There are exceptions, most notably devices in cut-in boxes that are held in place with Madison bars.
There's never a reason to tape a wirenut though.
About the only thing tape will accomplish is to leave a gooey mess for the next poor schmuck who has to work on it.
P.S. Occasionally, you'll read an article that recommends (or even demands) tape everywhere. These are almost always written by some sort of a sensationalist who is getting behind on his McMansion payments.