I live in Australia, but am expected to use US English in my work. I am therefore used to spelling "-ise" as "-ize". I was a little surprised to find that "enterprise" is almost universally spelt with "-ise". Is there any particular reason that this is the case for this example, when "-ize" is so widely preferred in US English?
For one, because the etymology is different.
-ise (-ize) is a causative suffix in formalise, realise etc. (to make something formal, to make something real...)
But enterprise is not "to make something enterpre" or similar (whatever that might mean). The prise bit comes as a past participle of French prendre (to grasp, to take).
Another answer is that enterprize is actually attested, and was apparently used more than enterprise in the second half of 18th century (N-gram viewer).