To those who think that being a parent puts you on a par with those with disabilities, in terms of difficulty in getting to the supermarket, ask yourselves this: if I don't have access to a special parking space can I physically manage to do the shopping? Not, "will it be difficult?", not "might I have to come up with a creative solution?", but "is it physically possible?"
Generally, the answer is going to be yes. Getting to that "yes" might involve making some changes to the way you do things, or the way you would like to do things, but you can probably get there.
For some people with disabilities, the answer to the question will be no. Some people simply can't walk the extra distance. Some people have such serious mobility issues that they can't get out of the car without being able to open the door to its fullest extent. Some people need wheelchair access.
For most parents, the lack of a special space is a mild inconvenience at best. For some people with disabilities, it is the difference between being able to do the shopping and not.
If the space is there, by all means use it. But don't try to suggest that it is vital to your ability to go about your daily life.