If I were to run D&D, you might find it refreshing.

[Rob Knotts]

On these boards? Supplements are more common. In general? They are more rare.

Just look at the sales figures. It's something like 3 core books are sold for each supplement sold. Now people who buy 1 supplement tend to buy more in the future.

One way to interpret that statistic is that most players tend to buy all three core books but only buy supplements that relate to the kind of characters they like to play. In my own group I'm usually the only one who owns copies of the game books (whatever game we're playing), but usually when I meet a new D&D group or see a game going on, everybody has thier own copies of the core books.