The death of the tagline may be overstating the situation, but there’s a growing school of thought that considers taglines as bygone marketing relics. There’s certainly evidence that taglines have diminished in importance.
"...the way we use taglines should shift from making declarative statements. In the ’70s, American Express warned “Don’t leave home without it,” and in the ’90s, Nike challenged us to “Just do it.” But now, as cultural power shifts from corporations to consumers, it no longer seems appropriate for brands to be issuing imperatives.
In fact, Nike’s vp of digital sport, Stefan Olander, recently said that the relationship between his company and customers has changed so much that Nike’s legendary tagline almost no longer applies: “People now demand us not to say, ‘Just do it.’ They say, ‘Help me just do it.’”
It's an interesting perspective. I'd argue the other end of the spectrum, however. The article states that "an effective tagline helps a brand stand out in the customer’s mind. As such, taglines work when a brand’s differentiation is derived from a product attribute." With so many companies today choosing names that don't convey anything about what they do, or even confuse the issue, a tagline could be a necessary tool.
For example, one of my recent client's competitors is a loyalty program called Belly. Is it just for food and restaurants? Fitness? No. I created a tagline for my client even though it wasn't on their to-do list because I thought it would help quickly define what they're about, and they said their target audience, small businesses, don't necessarily understand how loyalty programs work or could work for them. Boom! Product attribute = tagline.
I think the issue is more that many new brands simply aren't familiar with when to use a tagline and how it could help them.