Comment by NikolaNovak
6 years ago
I tend to use “How come you you didn’t use x?” Or even “how come X didn’t/wouldn’t work?”, and let my body language and facial expression indicate genuine curiosity,and maybe even perplexion at the scope of problem. I don’t feel Author considered the non verbal ways of communicating intent.
“How come” feels slightly lest antagonistic then simple “why” but that may well be regional differences
"How come" and just "why" coupled with fairly direct phrasing are a lot better than most of the rest of the suggestions elsewhere in the thread as of this posting, most of which seem highly passive-aggressive.