XII had those crystals, but I can't really remember how frequent they were.
There were enough to make fast travel easy and you also had the Strahl at various locations and the aerodomes.
I literally don't think I've ever used the Strahl.
Fast travel is absolutely necessary for an open-world game. I like the idea of having a handful of points, though – too many can make it kind of lame. I think XII and Xenoblade have done it best.
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