Some people argue that HFT provides liquidity for retail investors, but it's debatable whether that liquidity is real or not since it'll be gone during black swan events. At the same time HFT profit from uninformed/retail flow. So it's debatable wether the actual activity provides values. I'd say probably not.

But there can be indirect value in working in HFT, just like there is with other demanding jobs. There's interesting systems and ML research going on in the field - that's knowledge you can take with you and share with others. Some time ago, HFT was driving a lot innovation in networking, infrastructure, and systems.

Also, over time I've come to realize that "providing value" is really difficult to quantify. Does working in Academia provide value? Maybe if you get lucky and publish something that actually turns out useful. The majority of academics publish papers that are nothing more than noise - negative value. Does working at FAANG provide positive value to society? Again arguable. You may inadvertently end up promoting ads and misinformation. Not everyone does - but it's not guaranteed that you don't without realizing.

"Providing value" is subjective and most of the time it's nothing more than a story people tell themselves so they can feel good about themselves.