That's a great observation, and it's a question city planners and public works departments grapple with all the time. The choice between lidded and open (or partially open) public trash cans isn't random; each design has its own set of advantages and trade-offs.
Let's start with the obvious: lidded trash cans. The primary pro is hygiene and odor control. A tight-fitting lid helps contain smells, which is a major benefit in crowded pedestrian areas or near outdoor dining. It also acts as a barrier against pests like rats, pigeons, and insects, preventing them from scavenging and spreading waste. Lids also help with litter control in windy conditions, keeping lightweight trash from blowing out. However, the cons are significant. They can be less user-friendly; people might avoid touching a potentially dirty lid, leading them to place trash on top or simply litter. They also require more maintenance to open and empty, and they are generally more expensive to purchase and repair.
On the other hand, open trash cans (or those with large, easy-access openings) excel in convenience and accessibility. The barrier to use is virtually zero, encouraging proper disposal. They are also simpler and cheaper to manufacture and maintain. The major downsides, as you might guess, are the issues lids aim to solve: exposure to the elements and pests. Wind can scatter trash, rain can create soggy, stagnant messes, and open bins are a buffet for animals. This can lead to unsanitary conditions and increased scatter, ironically creating more work for cleaning crews.
So, what's the verdict? There's no one-size-fits-all answer. Many cities use a mixed approach. Lidded bins are often preferred in high-density urban cores, parks, and food-heavy areas. Open or basket-style bins might be used in fast-moving, high-traffic corridors where convenience is paramount, with the expectation of frequent emptying. The ideal system balances public health, user behavior, cost, and maintenance reality to keep our shared spaces clean.