It could be that there's just some kinda bad juju about going Warp 10. It might be that going Warp 9.9999999999999 is safe, and going Warp 13 is safe, but if you go Warp 10, you turn into a lizard and occupy every point in the universe simultaneously. That would explain why starships are often seen going faster than Warp 10 without lizardification happening to the crew. Warp 10 is simply the "brown note" of space travel.
EDIT to add: I can manifest the same phenomenon in my 1993 Isuzu Wizard as what happens with the Warp 10 'brown note.' At speeds below 65 MPH, the truck runs fine. But between 65 and 70 MPH, the truck bucks and shudders and makes burning smells. However, once above 70 MPH, it runs well again.