When I first started I used to call back when I could, sometimes a couple of hours later and would either have a punter asking me why I was calling back, sometimes this would be with abuse; the punter had understandably found someone else; or worse a female would answer.
I mention on my profile that I will not call back because not everyone has a dedicated punter phone, and to keep trying. I also mention this in my outbound voice message to call back later.
The exception, of course, is when the punter has let me know that I can call back at certain times.
It has nothing to do with laziness or whatever. It's about discretion.
Texts are easy to reply back to quickly as they can be easily be done when travelling or going about my daily life. I don't really want to be in a queue in a store discussing various strap-ons or other bits of equipment.
Cannot get hold of that person, move on and find another hooker.