Given how far the airport is from the city, this shouldn't really come as a big surprise, and it does not seem unreasonable to me. It's an hour (or more, depending on traffic) by taxi between the airport and the city. A free shuttle would be an expensive (to operate) freebie for a hotel to give away.

It's too bad there are no hotels near the airport (at least I don't think there are any - yes, I know there are "sleeping pods" in the airport, they look a bit spendy to me given the lack of amenities). If there was one (a hotel) close by, the cost to shuttle people would not be prohibitive.

This actually looks like a solid business opportunity: it's a huge airport, with lots of transit passengers. If someone built a reasonably priced hotel adjacent to the airport, I bet they would get a lot of customers.