Is this just something normal that I should ignore?
Yes. The bottom exterior molding of a car door's moveable glass is commonly referred to as a belt molding or reveal molding. Designs differ widely but in everything I have worked on, rain and wash water drainage is designed in this method:
Light and medium rainfall should not enter the interior, however pressure washing and hard rain with the car parked at an angle are not warranty-able leakage scenarios.
That being said, no belt molding is intended to stop all water. Just most of it. Some might call it a window sweep, and thats an appropriate term and description as well.
Drains exist at the bottom of the door shell. In many cases, these are holes in the metal with a rubber insert to keep dusy from ascending into the door while at the same time allowing any standing water in the door shell to drain. These drains must be clear, sound like your are but periodically check them like maybe twice a year as maintainence.
The "weather liner" is the final barrier. The plastic or coated papaer sheet behind the door panel that lots of folks toss out. It must be water-tightly sealed at the sides and bottom, to the door shell. Careful examination of the door shell will reveal the water flow path intended within the liner.
Everything outboard of the weather liner is designed to operate in an environment where moisture is present. From there inboard, it is not. Dismissed, do your homework!