It just happened that way in Greece and I suspect Italy too.
I thought there was a tax reason for this, i.e. Italian flying clubs not having to pay excise or other taxes in exchange for only supplying local aircraft. Maybe Africanpilot could comment ?
This is what I found on "women in aviation" from 5 years ago
The board of directors of the Italian Civil Aviation Authority has decided that any company applying for a mandate to manage an airport in Italy will be compelled to guarantee the availability of all fuels required by aviators, and not only JET A1.
The move has been roundly welcomed by AOPA-Italy president Massimo Levi, who has long sought such a requirement. Availability of avgas has been an even bigger problem in Italy than most other European countries and is one of the major concerns for GA pilots in Italy.
Massimo says: “This decision is very important for us. It does not mean that all major airports will make avgas available overnight, but it is likely that for the next summer season the problem will be resolved at many large airports.”
Avgas will remain a problem on small airfields managed by flying clubs as the fiscal regulations in Italy are so complex that many clubs do not have the means to provide the service. AOPA is working with the Italian tax office to try to simplify the regulations.
If by contrast, the reasons are not fiscal, but the industrial suppliers provide cheap gas in exchange for not selling to visitors, then it becomes a more problematic issue. But there's nothing to suggest this. Just bonkers Italian (and Greek) taxes - now there's a surprise.