In the construction tool world, I can go to my local home improvement store and rent a tool for as long as I need it, instead of having to buy the really expensive, but correct, tool.  In the software tool world, while some vendors offer free trial periods, others do not.  I have sometimes used the free trials to accomplish a task that is a one-off perfect fit for the tool but I probably will never use again.  It would be awesome if software companies would "rent" their tools for projects to those of us who don't have a budget to buy it permanently or don't have an ongoing use for the tool.