I don't know where you live, but to get a really good response to a party from people who live all over the county, you probably need amazing organization and to set up a whole weekend. Most people wouldn't travel for a one night party and fork out the cost of a hotel, food, travel (which is really high at the moment) off an invite on Facebook. you also need to check with each person individually and get a definite reply. I have travelled myself for a friend's 40'th to do this, but the whole weekend was organized, she found me somewhere to stay and so forth.
I think it's different for a wedding, though, that tends to be a whole weekend, but even then it's expensive to travel for that.
But people tend to get married only once (or twice!) in their lives, whereas people have big birthday a lot, if you have a lot of friends you might have, say, 8 such parties or weekends or events in a couple of years, surely you can see the obligation to attend is less.
I hate to say it but if you had organized a 'let's all celebrate our 30th' weekend, costed up, with people definitely in or out, then you probably would have had 5 old friends to celebrate with.
In general, I think house parties for one night tend to be attended by local friends, and that's what happened here. I wouldn't expect friends who live 200 miles away to come for a birthday party round my house, most of my friends have jobs and children (including with disabilities) so can't just up and go away, it has to be carefully co-ordinated, planned around the weekend date everyone can do. If you have a casual party which is on the date of your choosing, without consultation, most people won't make it.
I'm sorry you were upset, but I think your expectations of who would travel for this were unrealistic and not set up to facilitate that for them, and it's great one friend travelled a long distance! I also think it's a bit rude and dismissive to the guests that did come that you are writing nobody came to my party, they did actually, and family, and lots of people made a bit effort for you, you need to treasure these people more, as your long-distance friends may have partners, kids, move to Australia and seeing each other for random weekends will get harder, not easier.
No need to ditch your entire friend group as suggested on here. It was not reasonable to expect them to all to travel for this event, IMO without a lot better organization and definite replies.