Most of the developers do their works on localhost. I am using my ubuntu machine installed with apache2, mySql and PHP5 for my works.
If one of my clients wants to access my localhost to check my works, I have to either buy a host [still, it is the best idea], having large space so that I can add my development; but it costs time and money. Even if money is not a matter, none of the companies do the registration within an hour or so; or we have to find a free-host for php and upload the files [the worst choice], having very limited resources sometimes it won't work.