ELI5: Why does the season start so late now?

I follow the Michael Schumacher Facebook account and they do a "on this day" thing every day, for the last few weeks they've been showing many races from the early 2000's, even though the current season doesn't start for another week, today they showed Malaysia 2001 which wasn't even the first race! Also considering there are more races now a days why does the season start so late? Is it to do with the in-season testing ban?

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