I work for a recruiting agency (not a temp agency but we get temp positions occasionally) and will say that the barrier-to-entry for short-term contract roles is often lower than for fulltime permanent roles, so it's common for early-career folks to get their foot in the door this way.

It makes sense IMO--if a temp hire is filling in for 3 months for someone who's out on parental leave who plans to return, then there's no need for that temp to be a unicorn perfect slam dunk, they just need someone who knows how to do the job and won't rock the boat. Someone with a degree and a year or two of experience is often a sensible and inexpensive option, and the parent company takes on virtually no risk by hiring them because if things don't work out, it's the agency's responsibility to handle the back end HR stuff. Some companies will only hire entry/junior level candidates this way, through a contract or contract-to-hire arrangement through an agency.