Why must US Covid-19 vaccine be rationed at all?

Isn't true the US government has bought 'all available' Pfizer/ Moderna/ Johnson/Johnson vaccine to a current US stockpile by March 1 of another 300 + million doses, enough for all?
Why the delay to vaccine pass out until Autumn 2021 and into summer 2022?

Oku2021-02-23T11:55:10Z

Schumer, vaccines work, but you should keep wearing masks, even when you get vaccinated, as it will protect you, but does not stop you from infecting other people. So, when you get vaccinated, you should keep wearing a mask not to infect other people.

Schumer2021-02-23T11:37:16Z

if they work why is biden wearing a mask...

Anonymous2021-02-23T11:30:36Z

That was the old timeline. Now everybody who wants a vaccine should be able to get it by July. It is my understanding that the vaccines the government has purchased haven’t all been manufactured yet.