It's been done but the cost is very high compared to other materials because of the amount of specialized labor and only boutique builders offer one, the legs are really fat so it has poor aerodynamics so it's only suitable for off-road as a drop in replacement for a bicycle frame built for a suspension fork to account for the crown to tire distance and almost everyone has switched to suspension off-road. I've ridden some of the cheaper titanium forks and they flexed so much I did not feel comfortable riding them but have heard even the expensive ones flex quite a bit.

You seem like you'd know the answer to this question: why do so many aluminum bicycles have carbon-fiber forks?

I do not, I just have owned a lot of titanium frames and parts over the years and just read obsessively about the subject. :)