The main issue is that it is costly.
So, I've been considering various options including web-based software, some of which is subscription based, and not platform dependent (meaning, I get a subscription, you can use it on a PC, Mac, or Chrome device).
Recently I came across Smarty Symbols. This is an online, subscription based service or purchasable disc that provides access to over thirteen thousand illustrations. It alone may not be the solution to my question, but it is a really interesting service.
Smarty Symbols does not provide a a user interface to create boards so the user will still need something to do this, though it could be a simple word processor with tables.
What is unique about this service is that the user is allowed to sell products made with these graphics. This is not the case with any of the other vendors, at least not without significant royalties. Their library is huge, and if you still don't find what you need, they indicate that custom images can be created.
If you are looking for symbols with which you can publish a product, Smarty Symbols is a great solution. Or perhaps you don't need to own symbol software, but would like to "play" with some for a month or two, again, Smarty Symbols is a great solution.