With increased channels of communication, millennials find that cards symbolize effort and send them for “cardworthy” occasions. Colin Gray/Getty Images hide caption With increased channels of communication, millennials find that cards symbolize effort and send them for “cardworthy” occasions. While email, texts and social media companies from Facebook to Snapchat have made it easier than ever to send instant greetings, more people — especially younger people — are sending greeting cards. Over the past year, greeting card revenue has been steady. The greeting card industry could bring in as much as $933 million this Valentine’s Day, up a bit from last year’s estimated $894 million, according to the National Retail Federation. Greeting card experts say it’s younger people and millennials, in particular, who have been keeping the industry afloat. And they’re buying fancier specialty cards, often with personal touches. “For Valentine’s Day, I got my mother a pop-up card that had a little cartoon that jumped out like it would give you a hug with a speech bubble that said, ‘I love you,’ ” said Ben Leeper, 2...