If I were to briefly point out the reasons I am continuing, I would have to say the following.

- I am 24 years old, a normal age for doing a phd.

- I am working at a multinational corporation, so when I finish I will have working experience as if I was working in the private sector all along.

- I like (not love) my research topic.

I am also a doctoral student - just started. I am doing an industrial phd, this means that I am working for a company (8 hrs per day) and this work is put towards the topic of the dissertation.
I personally hate the academia (its a strong word but thats the true). Doing a phd in a research lab in a university basement is a waste of time for me, regardless the research topic. In most cases, you are being taken advantage of, and work overtime for nothing. This is not a healthy life, it is a perverted notion of someone that thinks that he is doing something great for himself.