That's because neither you nor anything in your diet (nor anything in your diet's diet) has titanium teeth and jaws.

The Earth's crust is 3.6% calcium, and we get more than enough of that in our diet...it's 5% iron. There's even a lot of titanium - fully 0.6%, much higher than 'rare' elements like carbon! [0]

I don't think we'd have any trouble getting it if the metabolic and biological systems that are employed to get us calcium were instead employed to produce titanium.

[0]: https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth...