My $.02.  
My snorkel broke while I was putting it on my mask before my 21st dive (boat).  I dived that dive and two more that day without it, and without missing it.  I bought a folding snorkel that I put in my BC pocket but have not used it on my ten subsequent dives, all boat dives.
I anticipate needing it on shore dives occasionally, but if it were rough enough to "need" a snorkel diving from a boat, it might be time to reconsider the dive, IMO.
I think of it in the same terms as my safety sausage, a small expense and a little bit of a nuisance, but it's there if I need it.  But I will not be having it hanging from my mask 100% of the time, no.