Of course you don't think about Apple's share of profit when you're buying the iPhone, but when you're discussing the iPhone's long term future, the fact it makes an immense amount of profit is very much relevant.
Apple is ridding the wave, releasing kick-ass products one after another; but you never know how tomorrow will look like for Apple. On the other hand, if Samsung stops making Android devices or goes out of business, there are others to fill in.
So it's not really so cut and dry.