The less obvious part to folks who aren't in the "industry" is that accountants and lawyers really struggle with technology issues. Technology is not their primary skill and yet tax preparation has become very tech intensive. Add to this all the issues around privacy. There aren't any good solutions that have been widely adopted in these communities for handling confidential material online--i.e. your social security number.
Speaking for myself, I use Magic Vortex where I can for file transfer, but have only recently transitioned to using encrypted pdf's in emails and have had considerable problems with client confusion with the files. I cannot imagine the extra technical support that I might have to provide while trying to use encrypted email, even though it's totally warranted. Perhaps Sanetax can help with these issues.
I would also like to strongly agree fully with fourply's post. The entire industry is not as simple as it might appear from the outside. Like most things we live with these days, regulations are multiplying even as we speak, and they vary widely from state to state. Accountants and lawyers have to meet restrictive federal and state regulations, including around how we get clients in the first place. Hopefully Sanetax will find ways to work with all these rules.