In design it’s important for things to stand out from one another so that they can be differentiated. If we don’t have enough contrast between elements things just blend together and get lost.
Contrast is becoming more and more important with design especially as we are more mindful of accessibility for people with visual impairment. Higher contrast is easier for all people to visually digest and therefore has a higher chance of converting.
In printing, contrast can present a different challenge. When there is not enough difference, the print job comes out looking all the same or some colours will create a halo between them. A good print shop will let you know when they feel either of these things will come up so that print files can be adjusted before starting the print job. Nobody likes a print job that turns out badly.
At the end of the day, contrast needs to be factored in to any design for print or web so keep this top of mind as you build things out or have your designer create them. I like to use the squint test and if I can still roughly make out the design when squinting then the contrast is on track. If everything blurs together, I adjust.