Because it's limiting. You voluntarily restrict yourself to this cultural gender duality when you don't have to. That dad wasn't "wholesomely masculine" when he was generous, he wasn't "toxically masculine" when he was abusive, he just was generous and abusive, and there is absolutely zero need to gender either of these behaviors.

On the other hand, if he was exhibiting unwarranted tokens of virility because he was afraid of being seen as not masculine enough, this is a toxic expression of masculinity and it is important to make the connection because it is directly linked with gender expression and gender perception.

People don't wear masculine or feminine clothes, they wear pants, dresses and shirts, they don't have masculine or feminine behaviors, they have individually defined behaviors. I know these terms are short-hands, but like all short-hands they are limited. And if you can't see yourself not using these terms, the problem isn't with my original post.