Just IMO, but with physical books you can open them and inspect the content, this might not be important for literature books but for more technical books you want to see examples. I am not from US and our online book stores do not allow you to electronically browse the books. Review might help, I wanted to buy a programming book for my son (Roblox sutff) and a review told me that the code listings are garbage and there is no actual care in the type setting of the book, now imagine I buy this book at the moment there is no such a reivew(and if the review was wrong then I avoided a good book), with a real store you can see for yourself, the downsides that the book selection might be limited for niche subjects.
Also I think is faster to evaluate the book if you have it in your hands, you can immediately notice if the quality is bad or good, if the fonts are maybe too small so it would be hard to read, if the content feels padded with tons of irrelevant stuff, if you like the art style or language of the author. Is the same like when you want to buy a phone or monitor, if you have it in your face you can imediatly spot things you don't like and see the real dimensions where if you have just some pictures and numbers in your face it is harder.(I bought a watch as gift for someone and when it arrived I was shocked how small it is in reality, there were numbers in the description but numbers felt ok for me at that time)