DISCLAIMER: I am not a doctor, healthcare professional, or personal trainer. Consult with professionals before beginning any exercise program.
It is better to offer no excuse than a bad one.
GEORGE WASHINGTON
I hear and read very few excuses given for not walking for fitness. If you physically cannot walk, that is a good reason for not walking. I was there once and had to do physical therapy to be able to walk like a normal person again. I know a lady who had an arthritic hip that made walking impossible. I know a veteran from the Army Airborne who has damaged knees who rides a bicycle instead of walking. These are reasons for not walking for fitness. Everyone else has an excuse, and they come in 2 categories.
1. Walking is too easy.
There are people who will tell you that walking is not exercise. I had that mentality for a long time seeing walking as merely the way to transition to running. Walking was a second class activity for soccer moms and old ladies at the mall. Something that easy just couldn't count as exercise.
I have been walking for a couple of years now, and I can tell you that walking is definitely exercise. I have logged more mileage walking than I ever did running. I have lost weight. It makes me feel good. I realized that I had wasted a good part of my life in the mental prison of thinking that walking didn't count as exercise.
There are idiots who will tell you that walking isn't exercise. YouTube has videos of these clowns. These folks tend to be either endurance athletes like runners and triathletes or steroid freaks who pump heavy weights and take kidney destroying supplements. Simple walking is a threat to them, so they have to throw shade especially if walking could hurt their business.
The people you should really listen to are the doctors and the research scientists who have the hard data. Walking definitely counts as exercise. This is because of the many benefits that come from walking. There are too many to list here, so I recommend doing a Google search on the health benefits of walking. The list is impressive.
2. Walking is too hard.
There are people who are physically able to walk but choose to do as little walking as possible. They claim that walking is too boring. They don't have the time to walk. They don't have anywhere to walk. You get the picture.
It doesn't get any easier than walking. If walking is too much for you, you are doomed. I don't think any of these excuses are legitimate whatsoever. People prefer comfort to discomfort. The problem is that comfort leads to discomfort as you lose fitness. Before you know it, just walking to the bathroom becomes torture.
Walking gets easier the more you do it. In time, missing a walk becomes the greater torture. It just feels good to get outside and get moving. Walking can be very addicting and pleasurable.
Conclusion
You will quickly find yourself putting people you meet into these two categories. I don't get into it with these people. If people are doing something harder than me, that's fine. If people are doing nothing, that's also fine. What I have found is that people are inspired when they see me out for a walk. They can walk for health and fitness, too. It doesn't have to be torture to count.
UPDATE: Here are some videos from some idiots on YouTube who claim walking doesn't count as exercise:
Find Out Why Walking Isn't Really Exercise In This Revealing New Video!
Walking Isn't Exercise
And one video from a genius:
Is Walking Really Exercise?