To prevent an accident from someone falling into an open basement window well it’s a good safety measure to keep the opening covered. Left uncovered and open to the elements, a well can become a bottomless pit where leaves and debris collect, preventing sunlight from filtering inside. More importantly, the debris can be an obstacle to using the window as an emergency exit if the need arises. A cover can also be an attractive decorative component.
It’s easy to be attracted to a lower-price cover; but keep in mind you get what you pay for, and the less expensive units can be one that cracks easily and will be damaged by sun, snow and rain. A window well made of a heavy material with the strength to withstand harsh weather conditions and the weight of someone standing on it is a better choice.