... during weekends, when the narrow street and the shops are very crowded.
Kalverstraat is one of the most well-known and most visited shopping streets in the Netherlands, but local Amsterdammers avoid this street because it is too crowded. Instead they go, for example, to De 9 Straatjes.
In the street are mainly retail chains for high street fashion, shoes and bags. Many tourists walk into the Kalverstraat without any purpose. They don't buy anything because they don't come to shop.