Just look at the requirements for the schools you want to go to and see if they require one, it's that easy.
If a school requires one, you can still apply and get a preliminary acceptance, pending you get the DO letter (I know VCOM-CC does this and some others do as well). When you do this, sometimes the school will help you find a DO to shadow.
But really, just do your research and make a few phone calls. It's not as hard as some make it out to be. You can do it!
Edit: OP, To answer your question: yes and no. Some schools are just different. I suggest calling the schools you're interested in. Getting a DO letter is VERY important though, even if the school doesn't require one.