Traditional power chairs are much bigger and heavier than lightweight manual chairs. They're a nightmare to transport unless you have a custom van with an elevator. They also can't handle curbs.

Ultralight manual chairs are often foldable, and light enough that you can transfer out of your chair into the driver's seat of a car, take the chair apart and put the pieces in the passenger's seat of a normal sedan. That level of independence is huge. Also, you can pop wheelies over curbs and other obstacles.

Finally, pushing yourself keeps you in shape, since you miss out on the baseline exercise from walking. Otherwise you decondition and get weak and fragile. Power chairs are for those who can't push themselves sustainably.

As many others have commented, every user's disability and body is unique. You're spending 16 hours a day in the chair. If it doesn't fit you, you'll get pressure sores or strain injuries. The cheap ones are for people who don't need to use them that much.