Could you elaborate more on the scenario why you want to delete the parameter?
Usually, you may want to either use an Audience to exclude the profile from targeting, or rely on profile persistence time. If none of this works for you, you may tune the "persistency time" by creating a more sophisticated audience with profile scripts.
I suppose the use case is the same for any time you would want to delete anything else in any situation. Not being able to delete something easily means that you can't proactively clean up things that are no longer used.
It also makes it harder to change existing rules. What if you have an audience that looks for an attribute to be present. Then, later, you want to delete that attribute in some situations so that it is no longer present for certain users. You can't do that. You would either have to update the condition to look at the value versus the existence of the attribute, wait for it to expire, or maybe write a script to change "persistency time" as you mentioned.