It may not directly help investors, who are buying into the company as a whole. It may just be an important tool to holding quality talent, to help Asana be as valuable as it can be in the long run.

However, from a monetary perspective, the investors are willing to buy in today at $1.5B. Option buybacks are usually at less than full valuation. Employees are trading value for a sure payout today. Therefore, using the money to buy back those options from early employees reduces outstanding shares and options and improves the value of remaining investors' ownership.