that actually sounds like a reasonable take-up
Given that a large fraction of individuals (even if we only take adults) don't have to fill in a tax form and fewer still are involved in financial dealings of a company, there's very little interaction needed with the burgeoning government machine. There is still a large number of people who don't want to use computers, don't like interacting with a "machine" or simply don't have the language skills (either as they're not good at reading/writing, or aren't fluent enough in english).
Where online services don't work is when you need to talk to someone, or ask (or answer) questions to determine what you qualify for, or what your entitlement is.