They raised $250m 2 years ago and have tripled their workforce since. Now they're losing money of course but why do they need to IPO if they raised so much money recently?
If they're not breaking even with revenue then that money starts to run out quite quickly.
Venture capital funds are for a limited time - e.g. five years. At the end of the time, the fund is liquidated - the companies are either sold, or closed down.
They can sell to another round of VC funding, sell to a competitor (who wants to "acquihire" the team), or by IPO.