Tradition and inertia.
The USA is proud to have the oldest and longest-standing written constitution. The fact it hasn’t been rewriteen in a long time help explain why there’s still an electoral college, slavery for prisoners (13th amendements), and weak regulation of campaign finance.
That’s interesting. Thanks for pointing it out.
My point is having a very old constitution isn’t much of a boast if keeping it as-is causes political issues.