I think all too often the, the CMS used to drive these sites is cause of poor usability.
Obviously, a CMS brings with it benefits to the organisation, such as devolved the creation of website content to the relevant departments, but this often leads to clunky pages as those writing them have little knowledge of usability and are constrained by the structure of the CMS.
My local council (London Borough of Islington) has brain damage such as 'to search planning applications click the 'planning' button on the toolbar on the left' - rather than providing a direct link in the content.
Saying that, the pages where this leads (https://www.islington.gov.uk/onlineplanning/apas/run/Wphappcriteria.showApplications?regfromdate=05-mar-2012®todate=05-mar-2012&DispResultsAs=wphappsresweek1) is clearly not within the CMS framework, and is a vanilla database driven query. It is piss-poor, being practically impossible to use unless you know the precise street address or planning application number, and looks poor as well. The 174 validation warnings for 1 page of content suggest there are several *per line* of HTML.
Their page for applying for a resident's parking permit is similar bad, and buggy as well. This is a service I struggle to use on an annual basis.
Pretty poor show - probably driven by an inability of the Council to hire good staff to build these sites.