Does your house have a great room? There are times you'll need access to a very tall ladder. Yeah, you can try to do everything using one of those utility poles with the sucker-grips at the end of them, but a really, really tall ladder can sometimes make a high-up job easier and safer.
Unless you live next to a friendly painter, chances are that you don't personally own a ladder high enough to do that kind of job. Fortunately, many home improvement stores including Home Depot, rent out extra-long ladders. Expect to pay about $20-$25 for a 4-hour rental. When height is what you need, a rented ladder can be your solution.