Another point about reasons for folk in the US buying (or at least, being offered by dealers) Murano weights could be the comparative lack of "generally affordable" decorative American millefiori weights.
Even now, there are fewer American paperweight makers providing millefiori weights as opposed to the more expensive, but quite superb, "Flora and Fauna" weights that have been popular in the US since Paul Stankard started the trend of "realism" in the late 1960s.