I agree with the above poster- It can be a great feature. Some gents are very easy to verify- if they are on Date-Check or are white-listed. On any given day that I'm working I get up, ready and could see someone pretty quickly if I have an opening in my schedule- so there is no down side to it in my opinion.
I know some providers take it as an insult that they don'w have a lot of advanced notice. When I get a "last minute" request- if I can make it work, I do. If I can't, I politely decline, and ask them to contact me again in the future. Screening still happens- and it can be a win-win for both sides.