Most tournaments Don't allow them, so they can't enter too many. Bots like texan Heat and Solar Flare are only allowed in Tournaments with really high safety rules.
Here's a vidoe of me testing out the rollbars, thought you might enjoy it:
S32 hit the nail on the head, pretty much all robotic competitions outlawed projectiles of any kind, Robotica however allowed the use of flamethrowers and I believe tethered projectiles to a particular length anyway nice job on solar flare Sonny_Resetti I should contact with HA to put up a list