It cares because: running out of cash is a bad idea for any company and running leaner says that you will have more runway. Whether or not it will be enough runway as perceived by that very same stockmarket will determine your share price. If there are no buyers for your stock the price will drop like a stone, so this is both a message to current shareholders 'don't sell, we'll make it' and potential buyers 'sellers are missing out on a great deal, you should buy our stock'. Of course this is more impactful if you are publicly listed (which Flexport isn't). But it will impact their ability to raise money, at what valuation that will happen and how existing shareholders will be diluted.
It may all not work and they may still go bust but that's their current messaging in ELI5 mode.
It may also be that Flexport - in spite of earlier messaging - is quietly planning an IPO. I think that would be a fairly stupid move at this stage but who knows.
https://www.cnbc.com/2022/05/17/we-can-be-one-of-worlds-bigg....
Another audience for these messages is their customers: if it turns out that Flexport's future is insecure they may well take their business elsewhere or stop considering using Flexport. That can reduce their runway even quicker.