yeah the thing every tubeless system even your cars,truck motocycles are clinchers and have a pressure where you will blow the tire off the rim.
A non tubeless tire aka standard casing does not have the stronger bead and sidewall of tubeless tire. They can not take the pressure. Notice how I said you can run higher with a tubeless tire, but then again why would any want to is beyond me?
For instance non-tubeless tire it will blow of the rim at at anything much past 35-40 psi
http://www.jensonusa.com/Bicycle-Tires/Maxxis-Ignitor-Folding-Tire-09UST tire will probably never come at any pressure
http://www.jensonusa.com/Bicycle-Tires/WTB-Dissent-UST-Tire-09It is still very much clinched in. The tube is in between but the tire still locks in place.
Another thing to keep in mind is that to much pressure can destroy a rim. Some of the lightest XC wheelset out there have warning about running more than 30 psi on them
http://www.notubes.com/ZTR-29er-Race-Gold-Wheelset-P782C57.aspxthen again people buying the ultra light XC wheelset would not be running a higher than 30 pressure anyways...... so its a moot point for them. I do not know what the limit of most wheel is being run tubeless but then again I never air up above 30 psi on my MTB and 50 on my cross bike so it does not really matter.