The sculptures owe their popularity in part to their history. In medieval times, pigs were herded from the farm to the market along Saustrasse ("pig street"), today known as Sögestrasse. It is also partly down to their appealing design and 'user-friendliness'. Children love to "ride" the large animals, and teenagers and adults use them as a seating area – the perfect spot for watching the hustle and bustle of the street.
It's so common for people in Bremen to arrange to meet up "by the pigs", that it's difficult to remember a time when they didn't say this!