They can be with decent search and if well organised. gov.uk works pretty well as it is and I suspect adding a chatbot would make it worse.
2. the nature of the problem statement "needle in a haystack" suggests obstacles to traditional text search, eg. too many false positives to be helpful for natural searches and challenges to constructing more specific ones.
language models introduce new possible solutions to this ie semantic search. poorly-designed chatbots could be worse than a basic search, sure
2. Yes, but its difficult to get a chat bot to function well over the wide range of services a government offers and the wide range of users who need government services.
One of the most annoying chatbots I have ever come across was on a UK government site. The DVLA. "lets tell you what you already know and not answer the question".
Possibly something well designed might make it easier, but I have found most of gov.uk to be very usable and helpful.
I'm very pro-ai, but we can improve the UI a lot sometimes, from the chat bot paradigm.
A chat bot, in theory, can help enable someone who isn't as familiar with searching, doesn't know the relevant terms, or lacks a sufficient literacy level to efficiently use an otherwise well organized site. The catch is that a poorly performing chat bot can just as easily mislead such a person.