I don't know anything particular about Ritchey or any other company, but there may be simple economic reasons for this.

Ti is expensive to buy and work with and due to various economic factors, US companies can't compete with China companies. If a relatively small company wants to make a distinctive frame or fork, the easiest way for them to do that is to use brazed steel. Titanium has high labor costs, CF has high labor and engineering costs, leaving only aluminum and steel. And of those two, steel is much easier to work with.

I've never had or rode a titanium bike, so you could say I don't know what I'm talking about--but from a cost/benefit standpoint, using Ti to make bicycle frames doesn't really make a whole lot of sense. Titanium's main quality is that it is fatigue-resistant. It's a great choice for using to make suspension springs or saddle rails/springs, but it's odd to use for a frame--unless you want a REALLY flexy frame. Which nobody claims to want otherwise?

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Semi-related: a few years ago I was browsing Alibaba searching for something, and ran across a Taiwan company making titanium MTB parts.
Pretty much EVERY METAL PART there was, you could get in titanium. Spokes, spoke nipples, clones of popular SRAM/Shimano front/rear shifters and deraillers (100% metal=Ti), ect ect.... They could even deliver saddles that already had titanium rails in them.
Cables and bearings was the only two things they didn't make.
It was a wholesale-only company, but they listed prices for their 50/MOQ. From them, it would have cost about $14,000 to assemble a MTB with almost-totally-titanium parts.