The Nokia 3310 is so strong, at least compared to smartphones, for a few reasons. First, the 3310 is a small phone made predominantly of quality, highly durable plastic. It has a tiny screen, which means there is less glass to break if it is dropped. And finally, there are fewer components inside since it is such a basic, simple phone.  Smartphones are bigger, which means more holes and gaps where water and dust can seep in. And they have significantly larger screens, which are more susceptible to damage, making them much more fragile than the 3310.