Anthony Acock was swamped at work and needed to make some space on his desk. So the assistant professor of graphic design at California State Polytechnic University, Pomona unplugged his desktop phone and stuck it in a drawer.

“It’s giant and has like five million buttons,” said Mr. Acock, 40 years old. “I don’t even know how to dial out on it.”

At home and work, technology habits have changed a lot over the years—and then there’s the office desk phone. With people carrying smartphones everywhere, a segment of the workforce has a hang up with the clunky office versions. Employees find them annoying and complicated, if they use desk phones at all.

Disconnecting may not be easy, as Mr. Acock found. After a few months, he said, an office manager noticed the phone’s absence and ordered it be put back on the desk.

“I was told to make an appointment with IT to get a training on it, but I just don’t have time for that,” he said.