What does this give you over jumping straight to the conventional questions? If the main goal of the interview is to extract signal about coding and general pro

What does this give you over jumping straight to the conventional questions? If the main goal of the interview is to extract signal about coding and general problem solving ability, why not just do the other two problems? Also, seemingly simple tasks can get people tangled up, particularly in an interview situation: there is a performance aspect to interviews, and this type of question can trip up people who are expecting your typical array/hashtable/linked-list style questions.