Many companies, especially publicly traded ones, may eventually decide the opportunity costs of working on something new or putting additional resources on something that’s more profitable is a better way to use those resources than using those resources on something that’s not very profitable.
I see this in my day job. I personally work with many small ISPs across the US and over the past few years a number have decided to stop offering TV service to customers. They made money on it but it’s wasn’t a lot and they’re often tired of dealing with the headaches that come it, like all the truck rolls related to it and the ever increasing cost of licensing channels. Just because they’re making some money off of it doesn’t mean it makes sense to continue to offer it.
I’m not saying that physical D&D books are anywhere near that point, especially since Hasbro and WotC have a lot of physical products but they will get to the point they start to think about it. If say it becomes a 20% physical and 80% digital split Hasbro execs may start to question if it would be better to spend the money spent on the physical side of things on something else that can generate higher profit than the low margin books, especially if they believe many physical book only holdouts would migrate to digital.