My Dodge truck's reservoir couldn't even be seen without removing the front end. I have no idea what size it was. My Ford truck also has a large one, but not as large as the Fiero. The 84 Fiero washer fluid tank is small, but that's because of the way they mounted the jack.
I have seen smaller tanks on vehicles but the Fiero's tank holds more than 2 gallons. It may be for the reason Paul stated. I know that during RFTH 23 yesterday there were a number of participants that reported their washer nozzles were unexpectedly squirting fluid on the windshield.