Eligibility is limited because vaccine supply is limited. Vaccination eligibility will be opened to others as more vaccine supply becomes available. See the vaccine eligibility description here: https://www.coronavirus.in.gov/files/Eligibility%201.5.21.pdf.
Please check ourshot.in.gov regularly for updates about who is eligible for vaccination. While the supply of COVID-19 vaccine is limited, the goal is for everyone to get vaccinated as soon as possible.