I think it's been suggested before. But they have other more important things on the agenda right now and it was the same case in the past too.
In case you think of writing or have random thoughts you want to jot down when you're out and not near a Computer, it was suggested that you use Evernote, Keep or some other free app to make notes or write stuff down, come home or visit a public library to work on the related hub.
Ohh I didn't know about the past app. I wish App was still alive. It would be much comfortable to go through notification and comments by fellow writers. To write a hub we can do it from computer or laptop there's no problem at all.
I also remember HubPages discussed about an app and decided not to develope it. Instead they are keen to optimize mobile website and to invest all resources in it. So I think there will not be an app (even if there was in the past). A good suggestion for HubPages staff, in this case, is to enable Google Chrome's mobile notifications in the website, so that we can get instant notifications through Google Chrome browser, just like an app.
Today, there are apps for almost every website. I wonder is there any app for Hubpages as well? It will be quite easy to stay connected with google app for hubpages. I have seen an app for hubpages but that one is paid....