Thank you for your question. It touches on a common aspect of modern urban design. Yes, many public park benches today incorporate specific features intended to discourage prolonged lying down or skateboarding. This practice is often referred to as "defensive" or "hostile architecture.
The most common feature is the inclusion of individual armrests between seating spaces. These dividers make it impossible for a person to lie down flat across the bench. Some benches are intentionally designed with a slight, ergonomic curve for seated comfort that becomes uncomfortable for lying. Others may use segmented seating—individual, separate seats with gaps—instead of one long, continuous surface.
To deter skateboarding, designers often use materials and shapes that are unfriendly to skateboards. Benches may have rounded, bulky edges instead of sharp, grindable corners. The supporting structures might be filled in or designed with obstructions that prevent a skateboard from sliding along them. The surfaces can also be made from materials that are too smooth or too rough for a good grip.
The intent behind these designs, as cited by many city planners, is to ensure benches are available for their primary purpose: sitting and resting for the general public. It aims to maintain accessibility and order in shared spaces. However, this approach is also part of a larger ethical debate about how public spaces are managed and who they are truly for, often criticized for being unkind to homeless populations.
Ultimately, while a traditional, flat wooden bench is becoming rarer, the modern park bench you encounter is likely a product of this complex balance between utility, durability, and social policy.