I am Greek and I live in Athens.
There are some things to take into consideration. For example the climate. It tends
to get really really hot here. The temperatures can go easily over 40c in the shadow. You can't wear a motorcycle jacket, nor boots with these temperatures. Usually I ride with my full face helmet on and summer gloves.
Also, it depends on your destination, distance and road conditions.
For example:
If I am driving just a few km down the road to get a drink, I might wear just my jet-type helmet.
If I am going with my buddies for long trip, on a highway or twisties, I usually wear my full gear, helmet, boots, jacket, gloves.
If your hotel was in Ios, you might have even seen me once or twice, driving my bike in flip-flops and no clothes from the waist up, but only for a few km at very low speeds, like a bicycle, from the hotel to the beach for example.
It doesn't mean that Greece is infested with squids!