My guess is enterprises were scared of going the SaaS route; partly as this model is still relatively new, but mainly because companies like to keep their data in house (or at least need the option to easily get hold of a regular backup / with some way to quickly restore it should the vendor go under).
Infrastructure costs. We had too many users on the free tier (5 users for free) and our server costs went through the roof. We didn't know how to find investment and my business partner needed cash so took a contract job.
