Not sure if I agree with this premise.
1. If the licensure requires a pair of shears on the truck, then why "require" your partner to carry a pair, before you "send him home" (wtf was that anyway? God complex?)
But however, If you have no requirement to carry shears on the truck, then i see your pointe.
I personally carry 2 pairs, but only because of the regularity of which i lose them. I work in a heavily traumatic area, and more than once ive sent them flying on the lap of a spineboarded patient with a flight crew.
Spare can't hurt.