Technology changes and develops constantly. Many people can feel left behind and so stop engaging with the digital world. Older people for people for example can feel that it's too late in life to start learning, or as they've managed without a computer or internet so far see no reason to start. Citizens Advice (2018) showed the numbers of people-around 60%-unable to complete online forms without assistance.
The ONS report (2019) shows almost double the percentage of respondents with disabilities identified a lack of skills or knowledge as a reason compared to those without (15%).
Security or privacy concerns were also given as reasons for non-use. A Carnegie UK Trust study (2015) highlighted specific concerns such as privacy, confusion about different options, and worries about spam and viruses.
The hard part is keeping abreast of new developments in the world of digital. I seems to change week by week?