Not really an issue I've ever had a problem with. My farrier is usually early, like I am scrambling when I get there because he's already set up, although he is comfortably getting horses out to start without me.
Things do come up. I've owned my gelding for 9 years (he's 9, do the math :)) and had him out on a 2 month lease to my former trainer and got him back a week ago and he needed a trim, I called my farrier and he came out as soon as he could (the next day) and my usually sweet, very easy gelding was fussy and cranky. Apparently, being handled almost exclusively by kids 6-12yo did not sit well with him. We patiently worked with him, and it only took about a half hour, but he is usually done with him in 15 minutes or less as my boy is so easy and just a barefoot trim. Once my gelding realized it was his old buddy Doug he was a happy camper.
There are no shortage of farriers around here, but there is a MAJOR shortage of GOOD farriers. The good ones do not need us, they have wait lists and turn down clients all the time, but we sure need them. If my farrier wanted me to kiss his feet every time he came to shoe my horses, I would. Just sayin :)
My vet is usually on time too, especially an appointment planned well ahead. I know that things come up and usually plan that they might be late. I try to be accommodating, because they will be when needed! Whenever I've had a horse that needed an emergency call, they were right there. One time I had a clinic appointment for my mare's leg and my barn worker forgot and turned her out in the neighbor's pasture and she had somehow gotten stuck on the otherside of a creek and I had to wade into the creek to get her, and had to swing by my house and change so I was not wearing wet pants and shoes in 40 degree weather, they squeezed me in to the appointments even though I was almost 2 hours late.
Stuff happens, to ALL of us!