>why does it always have to be a religious object if an object doesn't have a clear and distinct purpose attached to it.
Worth looking at how the Romans themselves thought. They were incredibly superstitious, overbearingly and obsessively religious (this is Roman Catholicism's roots), they believed in magic and spirits, constantly consulted oracles, augury, and other signs to make important decisions, and key roles in the Roman government was run by people who were also priests, in the Republic and early Empire most civic functions were also religious, and after Caesar they regularly deified their leaders.
Given that this object was clearly precious to its owners (found in treasure hoards/graves), wasn't used as a tool where it would receive any wear, and no one discussed it at all, a cult object would make a great deal of sense. Perhaps Gallic Rome had a regional cult these are tied to. There's a massive number of other Roman ritual objects, magic tablet, amulets, curse tablets, and other religious ephemera, the Romans really loved their cults and rites, if you have an unknown Roman object that's conspicuously not spoken about like these things, that itself is a fair reason to suspect the object might be used in secret religious/cult rites.