When you pipe the output, ls acts differently.
This fact is hidden away in the info documentation:
If standard output is a terminal, the output is in columns (sorted vertically) and control characters are output as question marks; otherwise, the output is listed one per line and control characters are output as-is.
To prove it, try running
ls
and then
ls | less
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D. Dominici, P. Gill, and T. Limpanuparb. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science, 468 (2145):
2667-2681(September 2012)