RSVP?

Today I have a bunch or running around to do. I am hosting a baby shower which I have no idea how many people are coming? Its a bit unconventional I just hope less show up then the amount of food we made. I would really not like it if more people showed up then food we have for them to eat....Why is it when you put in the time to send out invites people don't bother to RSVP? But you call them or see them out and mention it and they are like oh yeah we will be there... Ok so let me get this straight you get the invite and see that it has a date to RSVP and you don't? UMMM rude!!!! Have these people lived in a cave or on the moon or maybe they have never hosted a party. It makes it much more stressful to go from 15 people to possibly 30 or more but you really have no idea so it will be a fun party I just hope we have enough of everything. I love baby showers, I had many with my two kids and each were different some were just women some where both  men and women and some were elegant some BBQ's each one was sooo fun ...I just hope this one falls in to place. So if you are reading this when you get a invite in the mail and it says RSVP please do either if you are coming or not it is a very respectful thing to do for the host Thank you for listing to me complain I appreciate  it!!!