Pisses me off that it's never live on iOS and Android yet it's available on PC. Should be available across all platforms at the same time. Its not difficult really.
It is difficult, really. The patches have to go through the Apple/Android store quality checks, which is an approvals process that Blizzard has no control over. They submit the data to Apple/Google, and then they have to wait for it to be published on the store. Contrast this with distribution on Battle.net, which they DO have direct control over, which is why the mobile versions lag behind the PC version. If they could have simultaneous availability, they would. But since they can't, they do the next best thing. If you want to complain, complain to Apple and/or Google, because they're the ones holding things up. (But also, it's important for Apple/Google to do quality checks to make sure no malicious code sneaks by, even if it's submitted by reputable companies.)
The lie that is spread around everytime this happens is false. Blizz is able to push them out at the same time if they wanted but they don't. Games like Runeterra are able to push out both PC and mobile at the same time. This is a lie that needs to stop circulating. Blizz choose not to.