"Why consulting?" and "why us?" come up in almost every first-round interview. A strong answer has the same shape as a recommendation:
- Two or three distinct reasons, said up front: "Three reasons: the problems, the pace of learning, and the people."
- Evidence for each from your own experience: when did you see this, or enjoy it, or test it?
- For "why this firm", specifics only this firm could hear: people you spoke to, a practice area, the way it staffs projects. "Great culture and smart people" fits every firm.
The traps: reasons with no evidence, and three reasons that are really one ("I like problem solving, analysis and solving hard problems"). The checks here only look for those structural slips; what your reasons are is up to you.