While performance comes first, weight matters to me. My 13 ounce Prana Zions win over 19 ounce Kuiu Attack pants. In the end, the Zions also function better, but if function is the same, I will take the lighter pair every time.
If weight is not listed, with the number of gear options available, over 90% of the time I just exclude the item from consideration.
I'm fine with others not thinking like I do, and with a company not listing the weight. But, if a company wants my money they should make it easy for me to get an idea of an items weight while comparison shopping.