AIBU to expect friends to stick to arrangements?

[Time2change2]

Is it me or are so many people flakey these days? Lots of friends (both current and in the past) seem to think nothing of making an arrangement for meeting up (with or without DC) and then cancelling last minute.
I totally understand if there is a real reason - ie illness or emergency, but the reasons given are often flimsy and IMO should have been organised around already made plans- (my 6 year old has too much homework, we are tired, we need to go shopping, I need to run an errand so there won’t be time etc) These are arrangement that have been made a week or a couple of weeks in advance.
What it says to me is ‘my time is more important than yours and actually I don’t value your time (and friendship) much.
In arranging to see the other person I have usually said no to other family or friends for that day and in being let down my 2 DC are disappointed and I am left with no plans.
Why do people do it? Are you someone who often cancels and why?
AIBU to expect friends to stick to an arrangement unless an emergency or illness?

Family life is tough. People try to cram too much in. I'd rather my friends can tell me rather than stress. But we would usually leave plans flexible anyway. If tickets were booked, food bought or it was a day out yanbu.

If it is one to one, than no, I would never cancelled for flimsy reasons if the netting had been co firmed rather than a 'maybe we could get together' type of arrangement.

I will sometimes say I won't join group meetings of I don't feel like it (usually had bad night and feel totally sleep deprived and not in a social mood) but that because the group can still get together and have fun without me.

I totally get you OP, I could have written it myself. I have some friends like this. I just take it now that any plans made with them may or may not happen so I have a back up plan. It's always the same people. Funny thing is another friend is always apologising for being flaky when she's not in the slightest, she always has good excuse in the rare occasions she has to change plans.

It drives me crackers too. I understand last-minute changes when people have kids, but they aren't the worst.