A lot of the time IPO investors, both public and institutional, value company cash on hand at more than $1 per dollar during an IPO. An extra 500 million in the bank might make the company IPO for a billion dollars more.

Peloton is an example of a company that did a huge unnecessary fundraise before IPO. I'm sure it makes a bunch of numbers and ratios look better on paper. Psychologically, I think it also helps companies lock in evaluation closer to their IPO Target for when people look back at the history of the company.

It's pretty similar too the idea of inflating employee head count. You can say "we made $10 million with only 10 employees last year. Wait until you see how much money you're going to make now that we have a hundred employees"