The exhibition designer, like 95% of designers since the dawn of time, will no doubt say that it's important not to clutter what is essentially a visual experience with distracting type. I would counter, like 95% of editors since the dawn of time, that an event like this is meant to be read just as much as it's meant to be looked at and that if you separate the caption information from the picture you reduce understanding and enjoyment by 57%. (I made that bit up.)
It's the same in magazines. If given their head 95% of designers will make the pictures as big as possible before stacking up all the caption information and squirreling it away in the corner of the page. The posher (or the more amateur) the magazine the greater the chance that this will be the case. It's something that never happens in picture magazines like Hello or Heat because they know that when people look at a picture they immediately want to know who, when, where and why. Ideally they want to get all that information at once, not in a tiresome double movement.
I don't expect exhibition designers to follow exactly the same discipline but there's something to be learned, particularly in spaces where the low light makes anything but 24 pt illegible.
By the way, I learn from an 1877 book about street life in London that in those days all recruiting activity took place in an area near Westminster Abbey. Fascinating piece about it here.