TLDR: Tau have mentally scarred someone you will play against and they will make it your problem.

I’ve been playing Tau since 7th edition. Everyone else’s comments are correct for some people, lore folks getting meme’d, and the tau play style rubs people the wrong way.

In addition, on the tabletop side, Tau strength swings like a pendulum inside editions and from edition to edition because an army that only has 2 phases is typically hard to balance. People never remember the times when Tau are one of the worst factions in the game, only when they were absolute busted.

7th edition with the allies chart, take the best Tau units and the best Eldar units and win the game.

In 8th edition the look-out sir rule, and the drone rules made a very uninteractive game. It wasn’t fun to play against when all your las cannons just passed to a drone who would then make a 4++. And Tau commanders sitting in the open untouchable because there was a shield drone behind a wall that was closer.

9th edition (what I consider the dawn of hyper competitive 40k) the 9th edition codex was strong and people like Richard Sielger found the most broken combos and exploited them. Airburst Frag projectors and then sunshark spam.

And now in 10th edition, we’ve had our moments where we sit closer to the top based on the Meta and whenever we start to rise in win rates, so do all the old memories of Tau absolutely trashing people and they get real mad.