When to use thimbles instead of blocks?

[tolachi]

I'm curious when you would consider using a thimbe instead of a block. Apparently Moth's, 18' skiffs, and even some big boats use thimbles instead of blocks in parts of their vang purchase. I've also seen them used very nicely instead of blocks as twings and barber haulers. I'm wondering what criteria you would consider to determine whether it is better to use a thimble instead of a block. I'm guessing that low travel high load applications are one. I love how simple and failsafe this solution is. No moving bits, nothing to explode. Clean. See below for an example. All thoughts welcome.