You invite the water that is under and around your basement to collect in one place where you can easily send it somewhere else.
Waterproofing is preferable but not all basements can be waterproofed. Some examples: Ones with floors built without waterproofing, ones with old walls made of permeable stone, ones with below-grade entry doors for cars.
Sometimes a sump pit is a lot cheaper, and just as or MORE effective than waterproofing an existing basement with water problems.
"The basement is dry except where the sump pit creates a penetration" is incorrect. Without the sump pit the basement would be wet. The sump pit is part or a drainage system, usually perimeter drains that direct water away from the basement floor and into the pit. And yes, sure, without the rest of the sytem (drains) and without the pump, the pit all by itself would be an accelerator for water entry.