True ! my biggest gripe though too !! Can be a safety issue though, as you automaticly swerve to avoid the glass .
I have Armadillo's on my main bike , although I dont get flats I get plenty of glass slashes in the outer rubber through to the casing , To repair these I deflate the tyre some , hook out the glass & apply locktite 400 ? (used for making your own custom 'O' rings) or super glue (virtualy the same stuff but cheaper ) , press the edges of the cut/slash together till they're set (not long 60 secs?), leave for an hour & re-inflate ,seems to work most of the time .On my rainbike i've put tyre liners in , they help too , but they seem to make the bike seem slugish