Something similar happened to me OP. I invited school friends for my 18th, they all said they were coming, then the day before my party the majority of them dropped out (with no excuses given). I was angry because I’d catered for them coming and had wasted money.

Years later, I’m still in contact with the people who did come. Who have I completely drifted away from? Those who didn’t.

I think it depends on how close you are to the people who didn’t show. If they’re like your best friends, I’d be pretty upset and would tell them how you’re feeling. If they’re more like aquaintances, the way I see it, you don’t have to put in effort if they invite you anywhere.

Try not to take it personally (I know it’s hard not to!) and focus on those who did come.