a lot of companies are using agencies to fill temporary staffing needs, which usually end up being permanent if it works out.
I work in the marine industry most company will not take you on unless you go through an agency. companies are using certain agencies so its the only way to get your foot through the door. Ive worked for 3 different agencies, they all did things differently. So make sure you know what you are signing yourself up for.
Most are looking at filling numbers so they get there commission. I have found they are usually good at finding jobs quickly (within a week.)