What is a Tour Card in darts, and why can you lose it simply by losing any match?

The Professional Darts Corporation (PDC) grants a Tour Card every year to 128 darts players, which allows them to compete in all PDC ProTour tournaments, those being all Players Championships and European Tours (or qualifiers to the later events in case the player has not automatically qualified). Additionally, holding a PDC Tour Card offers further benefits such as automatic qualifications for the UK Open or participation in the qualifying rounds for the World Darts Championship, Grand Slam and World Masters, among others.


https://en.wikipedia.org/wiki/List_of_players_with_a_2025_PDC_Tour_Card

According to this site, you can't lose a Tour Card for just one loss. It looks like you lose it when your ranking is outside the top 64 at the end of the season (in January each year after the World Championship ends) and your two years have expired.

The Professional Darts Corporation has 128 Tour Card Holders each year. The top 64 each year following the World Championship hold a one-year Tour Card, alongside players entering their second year of a two-year Tour Card. In addition, players from Qualifying School plus the top two players from the previous year's Challenge Tour and Development Tour Orders of Merit have a two-year Tour Card.

https://www.pdc.tv/TourCardHolders