lets just correct that little goofball generalization.
Phones in general often have poor receiver/transmitters. Many consumers don't bother to research that part of a phone.
For people whom that part of the phone is critical to {people in rural areas, contractors who work in metal buildings) there are websites which measure that.
You could more accurately say that Apple has never put much work into that part of their line of phones. Apple has never been the whole market though.
Yes, initially, they pretty much WERE the smart phone market. Before them were the 'feature phones'. (Yes, some folks call Blackberrys and Palms 'smart phones', but they weren't. As anyone who's been tethered to a Blackberry knows.