It costs time and effort, something that disabled people often have less of.
Voter fraud is extremely low in the UK, and most of what does occur isn't stopped by these changes (the most common type is, for example, parents submitting a postal vote on behalf of their (18+) children without asking them), So here's a question for you:
If the number of people disuaded from voting due to the new ID laws significantly outnumber* the amount of fraud that's prevented by this law, was the law a positive change?
*To the point that it has a larger effect on election outcome
There's a lot more than just military data that needs a caveat here. Health records, criminal records, and a number of other categories of data that the government holds to provide public services need restrictions on access.
Even land ownership being public has downsides. Maybe I don't want my (hypothetical) abusive ex to be able to find out where I live after I sold up and moved specifically to get away from them.