I've been trying to find out if there has been some explanation as to why the O5 are still in the present day.

Didn't battle of atom show that if anything happened to them disastrous consequences would happen?

And on a side note is secret wars relevant if I just want read xmen stories. I mean apart from doom vs clips does it affect the X world in anyway?

There has not been a explanation yet. It don't make any sense.

I don't think you need to read Secret Wars. I haven't read it yet.

If everyone stops reading it maybe they will go away.

BOTA showed what would go wrong If they never left

At this point it seems like Marvel has no intention of sending them back, despite the fact they want to break their own time travel rules, which makes it harder and harder to believe they can be in the present for this long and then still go back.