As for people preferring William to his father - I think if you give an inch to the notion that the public should have some choice over their head of state then the idea of a hereditary monarchy starts to look pretty absurd.
Reminds me of when when the rules of succession where changed so that the first-born child would inherit the title (rather than the first-born son). Any attempt to reconcile the monarchy with the concept of equality seems a kinda humourous to me.
Early on, the Swedish king was elected at the Stones of Mora. The Holy Roman Emperor was nominally elected by prince-electors (who most of the time elected a Habsburg).
And even withing a hereditary framework, there are other alternatives to retirement in addition to outright abdication. An elderly monarch could for all intents and purposes retire and a let the crown prince (and I suppose in current British succession order, crown princess) rule, appointing them as a co-ruler.