iOS supports zooming the entire screen as part of its accessibility feature set. Though you have to turn it on, and the gesture is three-finger-tap and drag instead of pinch.
I have bumped into this countless times - street names too small, I subconsciously pinch to zoom, street names get scaled accordingly and are still too small for me. The solution is simple - just move the i<Device> closer to my face - but it's thrown me a couple times. Not sure if this is a UX error or just me being daft.
Unfortunately, I'm far sighted, anything closer than about 12-18" from my face tends to be blurry... I know I can/should wear glasses... but really, the phone is the only device I typically have a problem with generally speaking.
Working with a visually disabled colleague recently iI'm becoming all to painfully aware of how much this is the exception. For Web, apps, OS, devices, and more.