It may seem arbitrary, but there is actually some logic to this! Hopefully with this info you can make your own decision about what kind of PPI prophylaxis your patient needs.
You should treat someone with an actively bleeding ulcer with an IV PPI BID. But unless a patient has significant stigmata (such as visible clots, or active bleeding or gross melena), they do NOT need to be on an IV PPI. If they have slow or chronic bleeds (from malignancy, AVMs, etc) without the signs mentioned above, PO will be fine. On a related note, there is no evidence that a continuous infusion is any better than bolus dosing, so you probably shouldn’t be using a drip unless the patient is in the ICU.
Most patients will be fine on a PPI once daily, especially in the outpatient setting. In patients with high risk of rebleeding (you can use the Rockall score to determine if they are), you should consider using a PPI BID.