I got myself a ISO certified dive watch this week. I now understand why they are so popular. There are, I believe, three main reasons.
Tough
Firstly, dive watches are tough. They are built to take knocks in conditions where hard things like dive tanks and rocks are a constant threat. While most well made watches are tough enough these days, a dive watch is still designed against accidental contact in the real world.
Readability
Secondly, dive watches are designed to be highly legible in the toughest of conditions, murky waters are again a constant threat for diving. That being the case they are designed to be easily read.
Quietness
Lastly, dive watches are quiet. The side benefit of waterproof casing is that it means no water gets in and so little sound gets out as well. I remember the shock I had when I tried a Swatch Sistem 51. The all plastic automatic watch and movement could be heard without bringing the watch close to my ears. Watches with less waterproofing will generally mean mechanical noise will escape from the watch as well.
These are things that every watch should be regardless of being a diver’s watch or not.