Many biotech and pharma companies are now outsourcing all their medical writing instead of doing it in-house. See for example this news article about the giant Pharma company, Pfizer:
"All of Pfizer's data management is now outsourced, along with many other related functions such as data entry, monitoring, statistics and medical writing, said Thomas Verish, Pfizer's senior director of Development Operations, revealed at the recent Drug Information Association conference in Vienna."
No wonder CROs are hiring so many medical writers. If you are just launching your medical writing career, a CRO is a good place to start. There you can be exposed to different types of writing and obtain valuable experience.
See a list of CROs here.