Are you suggesting that's impractical? I never wore a dress on any occasion but I've certainly seen people combine a dress and a family bike. Then again I've lived abroad so I don't have typical American beliefs about the impossibility of riding bicycles.
Sure! Both of those are very suitable above-the-knee summer dresses and absolutely fine on a bike.
Below the knee, or full-length, and you start to have problems. Nice to have the option of an enclosed space if you’re going somewhere where the clothes matter.