Dealing with folks shopping around is part of many businesses and activities. Blocking them because they fit the pattern of window shoppers is not very proactive.
Let's take each case at a time. Just because a profile has pictures and stats of young man that doesn't mean he'll flake.
There you got it!
That's why some are blocking you, others might think you're less likely to hire them.
Have you thought about logging off and texting them to make plans?