Ategir has longer reach and therefore is well suited to be used with dodge which is how I use it mainly.

People tend to stick to the easiest / safest way to beat the game which is why you have a huge amount of players who cheese bosses, kite with a bow / arrow or use a shield.

Not everyone plays these type of games for the challenge but if that is your thing, you would definitely be looking to progress past being reliant on a shield.