This card is what makes normal monsters threatening. With high base attack and a quick-play spell that lets you take down most monsters, you can confidently normal summon any normal monsters without fear, or summon a normal monster and set a card to bluff your opponent.
Same reason Axe Raider is. Power creep. It was the highest ATK Level 4 (without a negative effect like Flash Assailant) at the time. Also, not sure why you're questioning that when Dunames Dark Witch is an Ultra with 1800. As you've noticed, we're now at the point we're getting Rare 1900s and Super 1900 Effect Monsters with relevant effects.