Question

Why are handcuffs like souvenirs

Answer 1

Handcuffs are like souviniers in a metaphorical sense. when using handcuffs you are normally capturing a villain. A souvenir is something that represent an era,time,place,event,etc. so an arrest can be considered an event therefore handcuffs are like souvenirs

Answer 2

Because the are cool and people don’t really have handcuffs, it’s just nice to have some handcuffs laying around to “arrest” your too drunk friend.