I am quite obedient, so when I see the rules of subs and they state that I have to agree to give them exclusivity on viewing, well, I abide by it. I send my precious piece in, and I wait to hear if they like it or not. If so, ace, if not, then I go to my next choice. Of course this means that if they respond quickly it's fine, but not all magazines are so swift. Elimae ♥ responded almost immediately with a rejection, and then with an acceptance, but they are the exception. I have been waiting a few months on responses for a couple of stories, and I may well wait a few more. In that time those stories are out of action, and in all probability they aren't sitting in a file having been read on receipt and now being considered, they are likely to be in a huge pile that one day someone will whizz through and send form rejections back on.
So, let's think this through, I have spent time and care writing something that I hope will be accepted by a magazine and published. Lots of these 'zines do not pay me a penny for my work. I am meant to be grateful that they will display my words. I am grateful. But when they "sit" on my story for ages before tossing it back to me they are disrespecting me, and every other writer that they do that too. If I know from experience that a mag is likely to take its time, is it fair enough to send my work elsewhere too?
Apparently most writers do just that.