there is not too many reasons why someone couldnt touch their chest. just drop the bar lower on the chest. tucking the elbows allows the bar to travel through its full range of motion. i can easily demonstrate this to someone and feel a tremendous amount of strain being relieved from my shoulders by just moving the bar down.
i watch all kinds of bench warriors, 1/2 repping their way to moderate weights only to be buried if the bar grazes their chest hair. remember, it doesnt count unless it touches the chest. thats the cardinal rule in bench pressing, from those that do it as a sport.
working through a sticking point is one possibility, as in the case of 2/3/4/5 board presses, but the for the majority of people this thread is talking about, that is their style of benching....all the time.