Change your hoses and fan clutch every 100,000km if you wish, other than that, they are not a servicable item. They fail, often without warning and we have little control over when or why they go, especially when due to manufacturing quality. You can inspect them as often as you like.
Oil cleanliness, on the other hand, we have a LOT of control over so it would be silly not to pay plenty of attention to 'servicing' it.
Hard to predict an unexpected, catastrophic component failure.

