Initialisation order, narrow demand and documentation difficulties, in my case. I wrote and discarded that class for Qt. It had tricky setup issues: Qt might n

Initialisation order, narrow demand and documentation difficulties, in my case. I wrote and discarded that class for Qt. It had tricky setup issues: Qt might need to test <N and commit to the result before the final N was known. It made documentation more difficult, since application screenshots would vary more. And finally, its niche was narrow. It only works if the number of items isn't known and varies across the threshold and the application developers don't have strong opinions about what to use.