California is using the psychological tactic of SCARCITY MARKETING to create demand for the vaccine.
https://myturn.ca.gov/
Scarcity principle in marketing works more like scarcity in the area of social psychology than in the area of economics. According to this principle, humans consider a scarce object more valuable than the one which is in abundance. Scarcity creates a sense of urgency and evoke people to act immediately.
This psychological outcome of scarcity is often capitalized by marketers to increase the demand of their products. They use terms like – flash sale, sale for limited users, till stock lasts, etc. to trigger demand among the customers.
https://www.feedough.com/scarcity-principle-marketing/