Because it system if government was setup with certain assumptions of the time.
Only rich landowning white men would be voting. Those men had the time to stay educated on world events because of either slaves or staff running their day to day business.
Certain customs were socially enforced simply as a matter of course. Scandal often meant resignation or recusal, or you would be ostracized from society entirely. If no one would work with you, your business, and wealth would die.