To lead the government and be responsible for it’s policies and decisions. The PM has to attend PMQ every Wednesday to answer questions from other MPs about what the government has or has not done. This holds the government to account.
Rishi has had to defend the government’s plan to deport asylum seekers to Rwanda.
To be a spokesperson for the government. They have to lead press conferences where they explain what the government is doing. Boris held press conferences where he has explained lockdown rules and covid restrictions in England.