When hand tilling a garden, why use a shovel? wouldnt using a hoe and dragging it do just as good?

You get the best of both worlds and use a Japanese digging hoe though you need a light hand for the weeding type of hoeing. It's one of my favourites.

Depends on if you want to turn the soil over completely or just break up the soil and mix the top few inches up. Even if you use a shovel, will still need to use a hoe or rake to level it out. And if you have turned the garden before, really no reason to do so. In my flower beds I just remove any old debris and dig holes to plant new plants. In my vegetable garden I'd use a tiller to chop up any old vegetation and mix it in in the fall so it would compost over winter. Then just use a hoe to did a trench to plant seeds in, or dig a hole for plants like tomatoes

The purpose of Tilling is to loosen the soil so the roots of your plants can grow easier and make healthier plants.

Using a shovel breaks the soil up down deep where the plant roots grow. Dragging a hoe just disturbs the top of the soil and doesn't do anything for the roots.

No, it wouldn't do just as well. Why don't you just try it for yourself and see?