I never really understood why companies ask this. They all know you also applied to hundreds of other companies and most companies are more or less the same from the perspective of someone who’s never worked there (assuming you’re applying to places in the same relative the same field). So what do they really want to hear when they ask this? Does it even matter what your answer is? If I gave a generic answer that could be applied to another company, would it matter?
This is just my opinion and depends on the company and industry. I never personally spend a lot of time research the company, but I do spend some time researching what they do exactly and look around their website. Be sure to know at least what their main product or service is, mission statement, any recent (positive) news event about them. I think interviewers just expect you not to be completely clueless about their company like you said they know you’re likely applying to a bunch of other places.
In my opinion, when they ask a lot of these behavioral questions, it’s just to gauge whether you’re a normal and agreeable person. They’re not looking for an out of this world answer or extraordinary passion for working at a particular company.