Question for people with joint accounts?

Do each of the signers on the account carry their own checkbook? Do you make sure the checks stay in range of each other (within 30) so they don't create a fraud alert at your bank? And why is it, one signer will sign all the regular checks for bills, but if they make a huge purchase like a car or appliance, the OTHER person signs it, so that the bank has NO record of that person ever signing checks? Just curious :)