For some companies (especially those, who are in business for several years already), customer reviews can do the trick. But what if you are the new one, struggling to catch up with already established competitors? You go for the visual proof, displaying the quality of your work and the awesomeness of the experience you are going to provide.
Some may say that escape rooms are still about mystery, that not-knowing-whats-inside can be a driving motive. It can be, on some occasions. But usually, the anticipation, the visualization of the upcoming fun at least doubles it. Just remember yourself planning a vacation - will you pick a hotel without photos? Or will you pick the most gorgeous one (within the available budget) and start daydreaming of vacation asap?