Some of this probably depends on the personalities involved.
I agree with this. Some people do as you do: rearrange their schedules to make time for the playdate, clean the house, prepare food, etc. Other people are more fly-by-the-seat-of-their-pants types.
I fall more into the second category. I am not going out of my way to make my house immaculate for a playdate. It is generally clean, but it will look lived in. I am probably serving light snacks, but short of making sure my fridge is not running on empty, I'm not doing any major prepwork here. I'll put out some fruit, which may or may not get cut while I sit at the kitchen island with the other mom talking over a cup of tea. There's always cheese in the larder, pretzels in the pantry, carrots and hummus in the fridge. But none of that requires any work on my part. My schedule is flexible and not planned out, so if someone were to cancel on me, I haven't really lost much. Yes my child may be disappointed, but we have playdates all.the.time, so a little disappointment now and then won't kill her, and we can then generally fill that unexpected time with something fun and unexpected, so general, no harm, no foul.
As to when I would cancel: certainly in the event of sickness, even when the other party would brush it off as just the sniffles; if my child were in particularly bad humor; if I had an upcoming event that I was ill-prepared for (going out of town, haven't packed; no gift for bday party that afternoon, etc). If it was a playdate that a great many people were attending, and I felt that our presence would not be greatly missed, I might cancel for lesser reasons (need to grocery shop, etc).
That said, I have learned over the years that there are people who fall into the first category, who are planners and schedulers and who do better with plans not subject to change. I have even lost a friendship over it. I have learned that this can be a sticking point, and so when making plans and indeed when making new friends, I am open about who I am, generally saying something like, "I'm generally always late. I'm terrible about returning phone calls. I'm scatter-brained and spontaneous. If you can handle all of that and take none of it personally, let's set it up."
Are those behaviors rude? Some people would say so. Personally, I feel that it goes to intent, if something is done with malicious intent, then yes it's rude. Speaking of myself, I don't feel rude. I have character flaws, these are some of them. Some people can handle them, other people can't. They can certainly be confounding. The thing is, I am more than that too, of course. I am a very good listener; a problem solver; a person who will always step up when a friend needs me; a very loving and engaged mother who attends to the children of friends with all the love and dignity I give my own child; and a person generally well connected in the community (not in a name-dropping way) so that I can generally always connect people with someone else who can fill a need for them.
The bottom line is that we have to learn who we are as parents and as people and find people who are compatible.