"...the public's ever present irational [sic] yearn for change."
Why is this irrational? The Tory party in 1997 was essentially unelectable. Stagnating after 18 years, with a fairly limp leader who was barely able to command the support of the party faithful, let alone the country. Of course it was important to boot that lot out, if nothing else because this gives the Tory party a chance to buck up their ideas, start over, reorganise, elect a new and charismatic leader, etc.
It's not clear that they've taken this chance, given, for example, the continuing split over Europe, but a party in perpetual office is in the long run as big a disaster as anything you've ever seen. What would even be the point in trying to persuade the public to vote for you? They will anyway, so you are free to do what you want with impunity. However much the Tory faithful might like to think otherwise, not everything they touch turns to gold, and so change, or at least a worthy opposition, is important.
On a local level it's the same. Safe seats sever the link between an MP and his constituency, as if, for example, the party wants a particular person in Parliament, they just give him a safe seat to contest. On very rare occasions even the safest seats turn out to be anything but (Portillo), but safe seats are as bad for democracy as safe governments are.