If I'm boosting 2k by 5db, it is more likely than not going to throw off the balance of that instrument. If you watch someone mixing on a real board you will see them playing with the faders after touching the EQ very often and that is why. It's no different than adjusting the output gain on a plugin, just different ergonomics.

If you already have a balance you like, why change it just because you're boosting something? Unless you don't like the balance and you're EQing for balance, which to me is mixing backwards and makes my head hurt to even think about.

I only use EQ for correction and sweetening, the mix is in the faders and pan pots.