Don't need any rules

"The secret we should never let the gamemasters know is that they don't need any rules."

― Gary Gygax

That quote is famously tossed around by people who don't understand it exactly the same way that I do. Sometimes its, in fact, misquoted that they don't need any books. Other times, it's interpreted that you don't need rules to play.

I think it's clear that what Gygax meant was that we don't need TSR published official rules, not that we don't need any rules to play. Younger players, and even many older players, either don't know, didn't do it this way, or have forgotten, how DIY the hobby was back in the 70s, and still into the 80s for some time. AD&D attempted, in some ways, to squelch that tendency, but that was partly because tournament D&D was very profitable for TSR in the 70s, and tournament play required regimented and consistent rules.

At home, however, the only thing that the game really requires to be played, is someone who gets the concept. You don't even need the basic rules, although it makes it easier to have a basic ruleset to start from. But if you understand that concept of the fantasy RPG (or any other genre, for that matter), if you've got a GM with a DIY attitude and drive to run a game, then he don't need anything else at all to play other than players.

Realistically, however, I don't think too many people are homebrewing their entire systems anymore. They're probably DIYing off of a base system that they like, either a 5e game, a Pathfinder game, or an OSR game (which is largely going to be based off of B/X or some other "early" version of D&D.) The people that are homebrewing are often selling it, and then people are using those games, i.e., Knave or ShadowDark, etc. So, realistically, 1) you do need rules, although you don't need official rules, you can write your own, and 2) most people aren't going to go to the trouble of writing their own.

What it does mean, though, is that there isn't any need for the various splatbooks or anything beyond the basic core rules. That you truly don't need and never did. Or, seen another way, given the DIY and third party way of doing things, you can buy someone else's rather than WotC's official D&D stuff to use if you want more product to consume. I personally like consuming RPG product. I've got a load of it. I don't care for more rules, though—in fact, I have moved to a DIY rules lite approach, although it's still modified based on someone else's work rather than truly built from scratch. But I like having stuff to read, especially "fluff" books and setting books and monster lists with new ideas for antagonists to potentially use. But I don't need them and never did; I just happen to be able to afford them when I want them, and I (slowly) have gone through reading most of what I've purchased.

This, of course, is a threat to the business model of TSR and later WotC (and Paizo) who aren't in the business of modest profitability by selling core tools and explaining the concepts to gamers, and then helping them proceed with their own DIY gaming going forward. Their business model is MOAR profits by selling stuff that people don't need, but which they enjoy just enough to keep buying it; or at least they feel like there's some benefit from buying it. This even gets to the point where they're trying to convince players that they do need to buy the continuing stream of product to consume, or they're not playing the game right and are at risk of.... being wrong, or something. I dunno. This state of affairs has gone on since at least the later 70s, when Gary Gygax himself said it repeatedly, especially with regards to pushing the abandonment of old D&D and use AD&D instead. So, yeah... it's an old story. Which is why, if Gary actually said the quote attributed to him above, he would have considered it a secret that they didn't really want GMs to understand or know.

So rulebooks can be cool. Fluff books—as far as I'm concerned—can be even cooler. But you don't need any of them. They're unnecessary luxuries. 

I thought of this because of Bob World Builder's newest video. He gets it.

To be fair, I think it's actually how a lot of busier, middle-aged guys participate in the hobby. They don't game nearly as much as they'd like, if at all, so reading products is their link to the hobby, and a way to participate and be a part of it still.

Which is cool. But it means that the industry needs to how and why people buy products if they want to have continual success in selling them. I think that there's been a lot of misunderstanding of that over the decades, including the business model that WotC are clearly trying to launch.