1) DUI checkpoints are actually law-breaker checkpoints. Illegal immigrants, non-insured, unlicensed, whatever. They don't just catch and prosecute DUIs.

2) They wreck traffic.

3) In nearly all cases they are easily routed around. Most (if not all) are advertised in a local media -- affording habitual day-drinkers the opportunity to avoid them easily. (this wrecks the REST of the traffic near the area, usually with panicked drunk drivers avoiding the stop)

4) They cost law enforcement time, for very little proven efficacy at anything more than accruing state revenue for expired tags and other small misdemeanors.