Except they didn't ask the students what they thought "makes economics important". Since the intended audience is undergraduate economics students, they probably don't need or want to be patronised with an explanation of why a professor thinks they should study the subject they've already chosen to study.
That would be silly.
What they did ask is, "what is the most pressing problem that economists should address?" If the intention, as stated, is to write a textbook that helps reduce the gap between economics as a theoretical discipline and economics as experienced in the real-world, then it absolutely makes sense to begin with what students consider to be the most pressing real-world economic issue, and use that as a springboard to explore the rest of the discipline.
In fact, starting with real world examples and applications, and gradually building towards fundamental, mathematical theories and models is the right way to teach any scientific subject. It mirrors the actual development of science, where fundamental theories are derived based on observation of the real world, and can be later disproved by new evidence. Introducing abstract and theoretical models too early not only risks confusing students, but it risks creating a situation where the models are considered intrinsically "real", and contradictory evidence is ignored. This issue has plagued economics, have taken abstract and simplified theories about markets and human behaviour and made them ideological dogma. The theories end up becoming lenses through which all evidence about the world is viewed, rather than imperfect attempts to explain the evidence.