Why do some clients put mascara on their eyelash extensions?

The whole idea of wearing eyelash extensions is so that you don't need mascara.  If you wear mascara with the eyelash extensions it can become strenuous trying to remove the residue  daily.  Further you may find that your lashes don't last as long  and applying mascara to the tips is your best bet. However,  some people will use the wrong type of mascara and then create a horrible mess.  I don't think it is a good idea.