It's because in lane if you make a mistake and catch 1 bind you're either dead, need to base, need a gank real bad... unfortunately any morg with 1/8 a brain knows how to black shield and walk away when see she's the jungler or mid doing something strange, and then if you break the shield she always has bind to stop you too... she feels real tanky for a mage.
the thing is she has no real downside, she has cc, burst damage, aoe stun ulti with lots of damage, fast aoe wave clear. Hence she is a real good pick/ban in solo queue. She's like Brand with a bind + black shield + spell vamp - a little bit of damage... (so basically 1000x better).
PS Pretty sure Kat isnt considered a Morg counter....