Why not? SE have so many sites and they are also increasing, if one of the site does not have any progress at all then why not delete it.
SE have proper scheme to check the progress , so there is no chance of wrong closing of site. Read this post for details about which site can sustain here and which have chance to got closed.
More sites doesn't means more growth , so there is no reason to take the burden of unsuccessful site on the shoulder of SE.
