Because people aren't as smart as you give them credit for. Abstract reasoning is incredibly rare in the population. Most people are wholly incapable of holding to a simple principle. Even on voat and poal there are tons of people who just cannot when it comes to the principles of freedom and liberty. Most humans fall prey to the "it's ok to do it to the 'bad guys'" mentality, and that's the whole problem. Everybody's a 'bad guy' to somebody so the day they get into power they go to work stripping freedoms from the 'bad guys.' A society that's truly free doesn't allow that, but the overwhelming majority of people want to do that. That's why the original Constitution had everything except the House of Representatives and the Vice President insulated from direct voting, but over time we've slowly eroded those protections. That's what Benjamin Franklin was talking about when he told the Constitutional delegation that they have a republic, "if you can keep it."