Some people need the past to be tangible. For them, the past doesn't just disappear into nothingness. It stains every object they encounter.
We're temporal beings, and our identity is constantly being shifted and affected. Collectors find Time's attack on their identity distressing, so they fight back by shrouding themselves with mementos, hoping to keep their identity intact and accessible.
For the collector, the past is not something to forget or to let go. The past is a companion. It's a friendship worth preserving.