It's hard to compare with any because it is a so-called "hidden disability". If you see a person with no legs in a wheelchair, you already know that running the marathon is out of the question. If you see someone missing a limb, you already connect what the person can / cannot do. So when you see an average person, you naturally assume that the person is fully capable of speaking on the phone and/or hold a conversation without difficulties. Something as basic as conversing with other people is something everyone can do, right? It's even harder because we all have good days and bad days. Some situations we speak like we were getting paid to do so, other situations we can't even say our own names. People that do not stutter can never fully understand the struggle because of just that.