You have been bowling for almost 10 years now and to me, the most common bowling etiquette that gets broken all the time is when a bowler is about to bowl or in their stance, someone starts to bowl beside them. This happens with people who don’t bowl in leagues and they don’t know bowling etiquette. You should wait until no one is on the approach so you can bowl. Most league bowlers know this but some people who don’t bowl in the bowling alley like that does not know.