Why would a parent look for a baby sitter in this manner?

I’m on the job websites looking for a job. Starting on Thursday and Friday of each week, people post that they need a baby sitter for that day or the next day. Some have 2 or 3 kids, some have only one. One woman stated she had friends coming in and her babysitter quit, but she was not going to miss an outing with friends. I don’t have kids, but that seems to be a dangerous way to find a babysitter. That doesn’t give them enough time to check anyone out, so who knows if this is a place child molesters are trolling?
I do know that is not how I would look for a pet sitter.
What do you think? Am I too distrustful, or are these people too trustful?