Variety of reasons..
- Left gets 110%+ turnout in districts that are 60%+ leftist
- Media will always ignore leftist scandals/corruption
- Left will bully the weak and uninformed with fear or guilt
- Leftists will go the extra mile and protest in your face to get attention, conservatives do not
- Left will accept foreign money to finance campaigns
- Many “conservatives” in polls are of the fiscal conservative/social liberal type, so they split their support
- Conservatives have no voice in national politics, so they stay home
- Republicans see conservatives as the reason for their losses
- Conservatives tolerate being beaten into submission while leftists scream and yell when a conservative simply looks at them.
- The fiscal conservative/social liberal crowd thinks nationalism is evil, so they willingly accept anti-American views to show they are tolerant
etc.
Americans are nominal conservatives but are in practice are operational liberals.
There is no penalty in voting yourself more benefits. And the Democrats profit handsomely from the status quo.