Titanium needs to be in a bigger tube with thinner walls to take advantage of the properties compared to steel - the very first titanium bicycles used the available surplus tubing from defense/aeronautics industry that was close to steel bicycle tubing size and were notably not great until they used slightly bigger tubing and better titanium alloys. Forks have a couple of design features that make it hard to work with titanium tubing, the height from bottom of headtube to where the top of the tire is has to have extra space for clearance or a tiny object or some mud will clog up the fork pretty quickly or cause an immediate stop in front wheel rotation, and that part of the fork has to be extremely stiff. Some of of the first carbon forks had a titanium steerer tube for a minimal weight saving and to make it easier to work with the stem attachment system. Several equipment changes to this part of the bicycle have come about in the last couple of decades to accommodate carbon fiber more easily. The market for titanium was just too niche by comparison to make those changes necessary.
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.
