[Neil Jones]

This only really applies to daily quiz shows that are on all the time, but isn't a reason why they don't tend to change their look is so that repeats can be slipped in without it being that obvious?

Can be but of course Pointless has changed one of its hosts, but the repeats still show Osman at the helm (on the daytime episodes anyway). I suppose in due course once they have a few series worth of the later/guest hosts in the can it'll be like Osman was never there. No end of quiz shows that changed hosts and then the original host(s) were never seen again on it for one reason or another.