Brazil has a similar system (gov.br), which provides access to almost everything you might need from the government, including notary services, public healthcare records, driver's licenses, consulate services abroad, income tax, social security, unemployment benefits, welfare benefits, and more.

I also understand the privacy argument that arises from consolidating all these systems, and I'm generally pro-privacy, including in some extreme cases. However, this service makes life so much easier across many dimensions of daily life, and I think it's worth it. I can only hope that the GOV.UK login achieves a fraction of this.