Perche

Because Italians take their holidays and family time seriously. Working on the weekend is not considered normal, so you have to pay extra for someone to voluntarily do that. It's a major reason for why Italians were just rated as the healthiest population in the world, where the average person lives well into their 80's.

It's a different country. You go there to learn some things from their culture, that might benefit you, not to expect and compare things to the USA.

i can imagine a typical tourist from the USA getting all steamed up because an Italian cab driver charged them an extra 2 euros for extracting them from their family on Sunday morning, when they normally wake up late, go to church, and then go for a walk with their family, and instead have to take them to the airport, only for the tourist to think they got ripped off because they had to pay an extra 2 euros for the weekend fee, which is very clearly published in all taxis.

If you don't want to pay the weekend surcharge for separating the taxi driver from his family, you can always take the train or the bus. It's all posted and visible outside the taxi before you get in.