Just staying at AKL doens't get you admission to Animal Kingdom. So, if you don't have a park hopper, and you go to AK in the morning and get done with everything by 3, you couldn't go to another park, unless you wanted to use your pass to gain admission to another park. Not a good idea, because you'd be wasing a full day's pass.
This is actually incorrect. Without the hopper option, you can't go to more than one park per day, period. Multi-day passes are based on the number of
days you're going to the parks, not the number of admissions. So you can't get a 10-day pass and expect to go to 2 parks a day for five days. Once the computer system records which park you've gone to first, if you don't have a park-hopper option, you won't be able to go to any other parks that day, regardless of the number of days you have left on your pass. The computer system simply won't allow you entrance into another park the same day, unless you have the hopper option. Make sense?
My advice is, if it's your first trip, you probably won't need the hopper option. Lots of folks never hop, even those who are WDW veterans. We always get the hopper option, but we like the flexibility because we go during the Epcot Food and Wine Festival. Regardless of which park we start out at on any given day, we always end up at Epcot, so it totally makes sense to have a hopper.
And it's important to know that if you decide to get non-hopping tickets, you can always
add the hopper option to your ticket after you arrive, if you decide you want to park-hop. It's a flat fee of around $50, regardless of the number of days on your ticket. So don't add the hopper feature if you only plan to hop one day - that costs you $50 per ticket! But if you hop every day on a 7-day pass, it's only about $7 per day.