And I assume that felons not eligible to vote; criminal, illegal aliens; and any others (e.g. already registered elsewhere) disqualified, have no more compunction against lying, than they do about breaking any other laws.
If no one checks, then there is no reason to fear that 'under penalty of perjury' boiler plate.
Checking keeps dishonest people honest...or else.
Oh, before I forget:
Would Daghlian take the same attitude about carding for tobacco (18) or alcohol (21) sales, since there is a sign posted stating that it is against the law to attempt to purchase underage; and that the establishment won't sell to underage buyes? That if they SAY they are of age, they must be, because "you assume people don't lie"?