When I have the disposable income, yes. And that may be part of what folks were keying off of in the other thread.
If the cost of the book isn't a big deal, then sure, why not? But, if the cost is an issue - I can get much, much more interesting reading time out of $50 of paperback novels than out of one $50 game book. Game books are a highly economical investment in entertainment if you use them, and much less economical if you don't use them.
It's the same for me. I consider myself a collector of interesting RPG systems. I enjoy analyzing and comparing system. And then there's Ars Magica, my favorite rpg system. It's been over a decade that I last played it, but I still buy every supplement.I know I have a small library of such books for a variety of systems, genres, and from a wide assemblage of publishers. I have grown to be comfortable with the fact that I like buying game books, even if I may never use them. I just like reading them and thinking about them. I sorta assumed most gamers were still like this, but maybe the gaming culture has moved on and left me behind, lonely and confused.
So elsewhere I ask people to convince me to buy the 5e books, and in the course of that thread, I have tried to be upfront that I'm not necessarily interested in playing 5e (at the moment) but am curious about the books. This has caused some confusion on the part of various posters and said confusion has in turn flummoxed me. Many don't seem to understand why I might want books I won't immediately use. I thought it was a fairly normal sort of thing to do.
Meaning... It used to be, that it was generally acknowledged that a good many game related books were bought but never actually used. I know I have a small library of such books for a variety of systems, genres, and from a wide assemblage of publishers. I have grown to be comfortable with the fact that I like buying game books, even if I may never use them. I just like reading them and thinking about them. I sorta assumed most gamers were still like this, but maybe the gaming culture has moved on and left me behind, lonely and confused.
So I am just wondering if my game buying habits have become an outlier, or are there still others out there willing to admit they do this?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.