Is it normal for the researcher/presenter to be absent from a conference presentation?

Being the chairperson for several conference sessions, the absence of a presenter allows us more time to share as well as more questions and answers... Very often presenters over-prepared with too many slides, so we are happy to have one missing presenter. :-) It is also not easy for me to request some professors to stop their presentation.

Maybe about 5 to 10% presenters missing in action. It could be delay in flight or work commitments etc..

The Conference may need you to register and pay first. They need money too...
What if more and more participants don't register?

Actually, conference paper with proceeding is not really well recognized. But it is still good for postgraduate students to have some...

One important purpose of conference is networking. You can also get feedback from other professors on your work, as well as possible future employment opportunities. Just have a cup of coffee with one professor; you do not know what you will get... may bring surprises to your future works...

Have you already applied for this conference?

If not, you shouldn't apply unless you know at least one of the coauthors can make it to do the presentation. Otherwise you take up a slot that someone else could have had, and it messes the organisers around. They might not look favourably on future applications from you or the coauthors to the conference.

Conference proceedings are a nice boost to the CV but if you're going to pursue that outlet you need to do it properly. Getting an abstract into proceedings is only half the benefit - the main purpose of conferences is to bring researchers face to face to interact about their work.