The key in the article is the term used "upper-tier" councils. A combination of limits on funding, limits on their ability to raise council tax, loss of revenue from things like leisure centres (as the article states) have led to a real squeeze on finances available to deliver those services that upper tier councils have to deliver. But note, this is not town and parish councils although the knock on effect is that town and parish councils are having to take on more services locally in some areas such as non-statutory services like the provision of litter bins, grass cutting and the like. Other than mismanagement, there is no reason for a parish council to go bankrupt and holding huge reserves is definitely not recommended and will be commented on by auditors.