That's how it works for me too using Money Plus. With your Microsoft Intellimouse with Intellipoint software installed, there does not seem to be a setting to map the wheel turns to CursorUp and CursorDown for the settings that can be mapped to a specific
application. There may be a third party application that can do that. I suggest that you use the PageUp and PageDown keys, or the right-side scroll bar, to move more quickly within the register. Those let me get thru the registers readily.
Regarding "why", it was costing significant money was the big reason, but there were probably some additional reasons.