This comes up most with families who feel their child isn't ready, academically or emotionally, to apply the year everyone else is applying.
A gap year isn't automatically good or bad. Admissions officers have seen thousands of them. What they're actually evaluating is what happened during that year, and whether the student can explain it with any clarity.
A gap year spent travelling with no direction, or simply waiting, usually doesn't help. A gap year spent working, interning, building a specific skill, or dealing with something that genuinely needed dealing with, often helps a lot. It shows maturity, and it gives the student something real to write about.
So the question isn't should we take a gap year. It's what would we actually do with it, and can we commit to that plan before deciding to take the year at all.