"Playing to Win" is for people who are trying to win at games. It's not for people who aren't. For those people who are trying to win, they should make (tournament-legal) moves that help them win rather than moves that don't.
You wouldn't think that would be even slightly controversial, but somehow it is. Even though playing to win is the most important concept in competitive games, it's also widely misunderstood. Let's untangle that now.
The Scrub Mentality
"Scrub" is not a term I made up. It sounds like kind of a harsh term, but it's the one that was already in common usage in games to describe a certain type of player, and it made more sense to me to explain that rather than to coin a new term.
A scrub is not just a bad player. Everyone needs time to learn a game and get to a point where they know what they're doing. The scrub mentality is to be so shackled by self-imposed handicaps as to never have any hope of being truly good at a game. You can practice forever, but if you can't get over these common hangups, in a sense you've lost before you even started. You've lost before you even picked which game to play. You aren't playing to win.
A scrub would disagree with this though. They'd say they are trying very hard. The problem is they are only trying hard within a construct of fictitious rules that prevent them from ever truly competing.
"That's Cheap!"
Scrubs are likely to label a wide variety of moves and tactics as "cheap." For example, performing a throw in fighting games is often called cheap. A throw is a move that grabs an opponent and damages them even while they're defending against all other kinds of attacks. Throws exist specifically to allow you to damage opponents who block and don't attack.
As far as the game is concerned, throwing is an integral part of the designit's meant to be thereyet scrubs construct their own set of principles that state they should be totally impervious to all attacks while blocking. Scrubs think of blocking as a kind of magic shield which will protect them indefinitely. Throwing violates the rules in their heads even though it doesn't violate any actual game rule.
A scrub would not throw their opponent 5 times in a row. But why not? What if doing so is strategically the sequence of moves that optimize your chances of winning? It's "cheap," though, throwing is cheap. And it's not just throwing, it's also a long list of somewhat arbitrary maneuvers. If you keep a scrub away from you by zoning them with projectile attacks, you'll probably be called cheap. If you do one move over and over, that's cheap. If you get a lead, then do nothing for 30 seconds so that you can win by time-out, that's cheap. Nearly anything you do that ends up making you win is a prime candidate for being called cheap.
Let's specifically consider the case where you do one move over and over. This goes right to the heart of the matter: why can the scrub not defeat something so obvious and telegraphed as a single move done over and over? Are they such a poor player that they can't counter that move? And if the move is, for whatever reason, extremely difficult to counter, then wouldn't you be a fool for not using that move? The first step in becoming a top player is the realization that playing to win means doing whatever most increases your chances of winning. The game knows no rules of "honor" or of "cheapness." The game only knows winning and losing.
"It's Not Fun To Play That Way"
This might be true, or it might not be, depending on the game. The scrub mentality is to make this claim for basically all games though so beware of that.
Some games don't hold up to high-level play. That's sloppy design in my opinion. A solid game holds up to experts playing it as hard as they can against each other. That way, the game can be fun for beginners and experts.
When a game doesn't hold up to expert play, it's degenerate in some way. There's only one good move or one good character, or one good strategy, or something like that. The game offers what appears to be a lot of fun options, but you don't actually get to do those fun options against experts, even if you are an expert too. So for this type of game, playing to win really will make it less fun, but that's not a problem with the players who are doing their best; it's a problem with the game. I wouldn't fault players here or complain to them that they are playing in a boring way. I'd complain to the game developer or play a different game.
There are plenty of games that become more fun as you get better at them, rather than less fun. With a good game, getting better and better at it reveals more and more depth to you, rather than exposing the game's shallowness. Games like Street Fighter or StarCraft are like this. My own games are also all designed for competition.