The physical thing mentioned but also some people just like the idea of owning the game and not having to worry about it being taken off the service or that if they dont wanna pay a subscription price one month, they'll still have access to said games. Game pass is a good deal definitely but its not for everyone.
Like all subscription service there will always be people that pay for a service they never use. Like you said on a earlier message people should learn to use the Pay as you go to max out the service and really get the most out of Game Pass. If use wisely Game Pass is a steal. When it comes to the ownership of digital copy, I get very skeptical do you truly own it therefore I tend to just focus on the experience and found the best way to maximize my gaming dollar.