Friend frustrations

I'm highly frustrated with a few of my friends right now. We've been friends for a long time, and live a few hours from each other. They always talk about how much they miss me and want to get together, but whenever I try to plan something or invite them to things, they decline or cancel at the last minute. Some of the events I've invited them to have been very important to me, and each time it's hurt my feelings that they've chosen not to be there. They are both wives and mothers, and as a wife and mother myself, I realize this makes it harder for all of us to schedule time together, but I've gone out of my way to be considerate of their needs and have notified them of events well in advance, so they can set aside the date their calendars and make arrangements for travel, babysitting, etc. The last-minute cancellations have been particularly frustrating. When I've purchased or made items for an event under the assumption they will be there, it's resulted in wasted money and time. I'm not sure that this has crossed their minds. Up to this point, the cancellations have NOT been due to sick children or other legitimate emergencies. I sense that at times, they don't feel like traveling to the events or to where I live, which irks me because I have traveled miles and miles over the years to visit them and be present on occasions that mattered to them. It also seems like other stuff frequently "pops up" on their calendars--and that they'd simply prefer to do those things instead. I don't get it, because when I was a kid I was raised that when you commit to something, you do your best to follow through and be there. I haven't really come out and told these friends about how their behavior is hurting my feelings. I don't want to be rude or make them angry. I have another friend who seems to only want me around when I can help them with their problems. At most other times, it seems like I don't exist to them. I'm a caring person who puts my all into my relationships, but I don't feel good about these people right now. Frankly, I don't feel like putting forth much more effort.

Thanks, SUSIEDQQQ. I just told one of the girls that it's up to her to let me know when she's available and to set up a time for us to hang out, if that's what she wants to do. We'll see if anything ever comes of it. I appreciate you taking the time to offer some advice!