Because Harpie's Pet Dragon is an Effect monster that has an actual effect?
(Cyber Harpie Lady on the other hand, totally should have been changed into a vanilla, considering the name thing isn't treated as an effect, meaning they could have done it like Summoned Skull is now)
Well, it's actually not that necessary, you just need it to deal damage by direct attack.
But yeah, protecting it would be easier if it has higher ATK.
If this card was released much later instead of in the first two years of YGO franchise in Japan, this card could have been released as a Union monster, probably.
Although, Union is so terrible, it isn't much of an upgrade over being a vanilla.
Not all Spell/Trap can be chained. Wall of Disruption for example, since it can only be activated in response to an attack.
But nowadays, most staple Spell/Trap cards can be chained to this card, so yeah, this card is still useless.
Trust me, this isn't even the worst PSCT konami ever made that actually creates problem than solving any, if you want that, look at the redundancy in Dark World monsters' text
Yeah, this card's effect is actually far more useful than the Tuner status.
The Tuner status doesn't even need to be there and this card would still be just as useful lol