That didn’t really help either. Why would someone want to enforce playstyle at all? Why is that a good thing to do?
Let's say you have a player who came from AD&D 2e, where enemies tended to target Fighters, not because of any mechanical reason, but simply because that's what Fighters were for. Switching to 3e, the player suddenly finds enemies ignoring the Fighter in favor of higher priority targets like the Cleric or the Wizard.
"Wait, what's going on? The Fighter is supposed to protect the other party members!"
"There's no real reason for them to do that. Easier to take them out rather than deal with the high AC and mediocre damage of a sword-and-board build", someone replies.
"This is wrong, the rules should make enemies engage with the Fighter!"
"Well, you could build a Fighter to do that, kind of, if you used a spiked chain and..."
"No, no, a Fighter shouldn't need a gimmick weapon to do things like that!"
Later in 3.5, a few ways to do just that were added to the game, like the Knight class, or some of the stances from the Tome of Battle, but this still wasn't a stated ability of the Fighter.
Perhaps this hypothetical player will approve of a Fighter who actually can "tank" for weaker party members, and thus embrace 4e, feeling that the game now "feels" more like the D&D they remember.
At least, that's what I assumed at least one 4e dev thought. Certainly, it's likely easier to design monsters and encounters around a party with balanced roles than four or more players doing whatever they want!
Of course, as history shows, far more people wanted Fighters to be armored brutes dishing out massive damage than actually protecting anyone, a trend that persists to this day.*
*Just ask yourself how many people play Cavaliers, who have a heavy defender theme, as opposed to other subclasses, if you take umbrage with this statement.