Leaving without notice

In the last month or so, the agency I work for has had a handful of people resigning immediately. I understand change over and moving on to greener pastures however, only one person has kindly given two weeks notice. It puts unnecessary pressure on teams and your former coworkers and makes the situation so much worse.

My Gen X brain wouldn't consider burning a bridge that badly in a small industry...is the mentality of employees are changing, do we no longer value our professional reputation?

Would love to hear others perspectives.