Also, posters are beginning to join the modern trend of using quick-response codes (QR codes), which can be maximized for easy communication/interaction with prospective customers.

Information like location, email address, phone number, and even URL can be communicated to the public by simply creating posters with bar codes for people to scan. Hence, posters can tell a lot while saying so little and expending less. 

Finally, posters are catchy and vivid. Many of us still remember images of posters from our childhood. This is because posters appeal and engage the mind. A well-designed poster printing could earn a place in the softest spots of a reader's heart, and a heart like that would very likely remember and chose the brand.  

As long as humans have eyes, and the streets have humans, and humans ply highways, posters will remain a valid and effective means of advertising businesses, and by extension, helping investors to earn their ROI.