Legally it is not clear whether you want tea or a "cup"of tea, lolz.
Actually, it sounds stupid but it saves time of the authority / department to whom the document is being submitted. Like when we apply for visa, they have given standard formats, application form, with further use of specified formats e.g. Date as mm/dd/yyyy, name as surname, middle, first etc.
That is why they insist on those formats which have already been accepted by them.
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