First and foremost: every foot and everyone's hiking preferences are unique. Use what works for you.

What might you be missing out on with a street running shoe? Depth of grip and (possibly) ability to handle sharp rocks sticking up out of the trail.

The kind of grip you need can be very dependent on where you hike. In England, hiking around in bogs with soft ground, hard nubs are preferred, but those hard nubs suck on wet slick rock. Hiking on dry, groomed trails don't need much grip at all. The soft nubs preferred on many trail runners are nice, but they sure wear off pretty fast.

If you regularly hike in areas with lots of rocks on the trail, street runners may leave your feet bruised pretty badly. Of course, many lightweight trail runners won't help you much either. Trying to find trail runners with an honest to gosh rock plate is getting more and more difficult.

Lots of people use street runners hiking. If they work for you, why not?