You are making a massive assumption here about how easy it is for everyone to arrange childcare.
My parents are both dead, my mother never even met her grandchildren and my dad died soon after my first baby was born. My husband's parents live on another continent. So, no, we didn't have grandparents on hand to step in when we needed childcare. If we wanted to go somewhere, we had to work around the practicalities ourselves. There was no convenient reserve army of relatives waiting in the wings. DH and I didnt go out on date nights together for over a decade due to this.
And I think your examples are a false equivalence. A hospital appointment isn't the same as a social engagement, and a milestone birthday or a concert someone desperately wants to attend is a specific event that may have been planned months in advance. None of those examples proves that arranging childcare is always straightforward, affordable or even possible. For clarity, any hospital or GP appointments I had, had to be arranged during times when my children were at nursery or school as I stated above, my parents are dead and DH's parents live abroad. DH was working crazy hours at that point to ensure his business got off the ground.
More importantly, you're assuming that because someone might manage to arrange childcare for one event, they can necessarily do so for another. Childcare isn't an inexhaustible resource that parents can summon whenever something important comes along as others in this thread have clearly stated. It depends on availability, cost, work schedules and the circumstances of the people involved.
You keep insisting that people are missing the point, but I think the point is perfectly clear, its just that you seem determined not to acknowledge it. OP wants to feel valued, and she associates that with her friends making a particular kind of effort. The difficulty is that she's treating their ability to arrange childcare as a measure of how much they care about her.
People can value their friends enormously and still have constraints that make certain arrangements difficult. And people can make plenty of effort in ways that aren't necessarily the ones their friends would most like.
Wanting to feel valued is entirely reasonable. Assuming that someone else's inability to accommodate your preferred arrangement means you aren't valued is quite another thing and that is the exact point.