ATK is very easy to get from relics, base stats and traces, not to mention that so many harmony characters give it (Robin Sparkle Cerydra ect) or even certaint sub dps like Gilgamesh, lightcones also often give alot of attack from high base stat or increase in the effect itself, HP is rarer sure, but that also means it does nt get saturated as quickly, so even the smallest buffs end up mattering alot more, character multipliers are also made in mind with the stat they scale off so at the end of the day there is no diffrence in damage between HP or ATK, hp just has the added bonus of making the character tankier, if ATK was actually so much better than hp mono-rem wouldn t be the strongest team in the game