Because there would be very little feedback from Religious Studies into other fields on what words are acceptable. There are disagreements on terminology within academia in the same sub-field (I saw this in even programming language research).
The "technical" usage is simply the normal usage of the word for anyone who mostly reads books published prior to the 1960s.
This article "“Cult” in the Study of Religion and Archaeology" in ASMA (https://www.academia.edu/5061036/Cult_in_the_Study_of_Religi...) has a pretty good discussion.
Here's an article from a text book on "Archaeology of Cult and Religion": (https://www.academia.edu/13590600/2005._Archaeology_of_Cult_...)
You can see a working usage in "A Problem Oof Definition: “Cultic” and “Comestic” Contexts in Philistia" (https://www.academia.edu/1868319/A_Problem_of_Definition_Cul...)
I haven't read the books, but there's a couple books covered in this review from AJA on the topic: https://www.ajaonline.org/book-review/619
Modern archaeology makes some odd-seeming linguistic choices to try to avoid implying more than they actually know; part of that is avoiding "religion" in favor of "ritual" and "cultic practices", because "religion" implies a whole lot of stuff that artifacts just can't see.
No: the audience is BBC article readers so the meaning is defined by that audience. The BBC is not a technical journal of archaeology, and if they want to use a technical term then they need to explain it and avoid using it in the heading. “cu*t” is wildly incorrect for the audience here.