Craiglist design actually sucks. When I first used it, the whole thing was almost revolting from design perspective. Where some people see simplicity, others see utter lack of modernity, friendliness and affordability. I still can't get some of my relative to use it (they ask me to post on their behalf!). Before you cite page counts, revenues and unique users, think about how many people are not using it despite the fact everyone has heard about it and everyone has a need to sell something on and off. Amazon UX is almost complete opposite of craiglist but is usable by much much wider audience.

I agree with you, but I still think they could benefit from at least having an app that loads their website. Craigslist is represented in app-stores by unofficial 3rd party apps that aren't very good. Users may have bad experiences with those apps, which Craigslist may want to prevent or control.

Some people might think (incorrectly) that their lack of presence in app stores means the company isn't focused on mobile or that their platform is not intended to be used on mobile.

There are benefits to having a mobile app over just a mobile website, such as mobile notifications, consistent/better authentication, being featured on users' home screens (next to LetGo, OfferUp, etc.) instead of hidden away in a web browser app. I would think that Craigslist would find their users to be more engaged with an app.

That is the correct answer - provided that your parent was serious.

I cling to the hope that your parent was actually joking.