In some companies users are not allowed to download and execute ActiveX controls from a web server. As the HtmlPlaceholderControl edit component consists of an ActiveX control this can cause significant problems as special permissions would have to be given to these users to let them work against MCMS.
An alternative to this would be to preinstall the ActiveX controls on the client machine. This can also be rolled by providing and MSI package and then automatically be installed through SMS.
The following article outlines which files need to be preinstalled.