Without accounting for inflation makes the number arbitrary. Might as well report it in Chinese currency and claim victory because the number is now bigger then those movies that were measured in USD.
Inflation in the US could spike tomorrow, and suddenly we could see multiple films earn $5 Billion a piece.
Edit: I do realize plenty of factors over the years affect a film's box office take aside from inflation. Adjusting for inflation does not by any means paint an accurate picture or create a truly fair comparison.
But it is a step in the direction of fair isn't it? Without the simple math of inflation calculation you're really out in the woods on what those box office charts spanning decades mean. In an exaggerated case, the US could undergo hyperinflation tomorrow to the point that a banana costs $300, but minimum wage becomes thousands per hour. Suddenly every single film that year beats Endgame. Will people hail Sonic 2 (2021) as the great film that beat endgame in the box office? Of course not, they'll have to go back to inflation calculations for the chart to mean anything at all.
I'm just saying why wait for an exaggerated case to compensate for inflation? What reason is there not to use it now other than to generate more frequent clickbait about new meaningless records?