If you have a tire blowout on tubulars, as long as you're not already going sideways, the tire sticks to the rim, giving you at least some chance of riding it out.

On clinchers, you are immediately faced with trying to maintain control on 2 skinny metal rails of death, while the flat tire squirms around unpredictability, constantly threatening to jam up in the brake calipers.

The last clincher blowout I had was 2 weeks ago (new tire defect), and even at 10mph (on a corner), it took every ounce of my bike handling skills to prevent from doing a header.

In contrast, my last tubular blowout was due to hitting a fist-sized chunk of metal in a tunnel in the dark at 40 mph. Immediately on exiting the tunnel, I faced a slippery reverse-camber corner with a completely flat tubular tire.

No drama: I just rode it out while the wheel made some muffled clanging noises.

If that would have been on clinchers, I would have never known what hit me; I would have next awoken in a strange bed looking up at the calendar on the wall wondering why the year was: 2021...

Anyway, this safety benefit is the key reason why elite-level riding will always be done on tubulars, plus the insurmountable weight benefits.