Why aren't FingerTrees used enough to have a stable implementation?

Question

A while ago, I ran across an article on FingerTrees (See Also an accompanying Stack Overflow Question) and filed the idea away. I have finally found a reason to make use of the

Answer 1

Ignoring your Finger Tree question and only responding to your further explanation: did you look into Data.Text.Lazy.Builder or, specifically for building HTML, blaze-html?

Both allow fast concatenation. For slicing, if that is important for solving your problem, they might not have ideal performance.