It's not laziness at all. It's simply how language works. The noun 'quiz' came to mean 'a competition in which participants attempt to answer questions'. Once such a word is established it owes no loyalty, linguistically, to other worRAB with the same combination of letters.
Quiz competitors felt they needed a verb to describe this activity and, it is natural, that 'quiz' was taken as that verb. It is very common in the English-speaking world for a verb to derive from a noun where no such verb had previously existed.
A previous poster said that the quality of the first quarter-final was not as high as he/she expected. I found the questions today harder than those found in the 2nd round and, I suspect, most of the competitors would have struggled a little on that set.