Thanks - that enabled me to do some further research. It looks like it is a hangover from last year when they banned all overhead baggage as a pandemic-related safety measure.
The rationale appears to be to reduce passengers faffing around with their stuff (as they often do) causing bottlenecks and more opportunities for the coronavirus to spread.
The Italian consumer association Codacons was quoted in one article as follows:
“In this area, the Italians are among the most unruly travellers in Europe, causing delays and queues which today would fuel the risk of contagion.”
Last edited by NeilMaybin; 29th Aug 2021 at 18:32.
Reason: Layout changes to make clearer.