Well my dad always told me not climb trees... you bet I did, and got hurt many times. Never rode a bike with a helmet, although I was encouraged to, and got some bruises because of that. But those are acceptable risks, because it was only my neck on the line.
Now If I'm responsible for multi million dollar machine and 20 people on board, that's a bit different story. If you don't want to fly in immersion suit, even knowing that in case you won't have a raft, you will hit second stage of hypothermia in lest than an hour, well thats endangering everyone in a relatively small way. But risking being knocked out mid flight is what I call poor risk assessment.
I found the birds to be a major problem because of their unpredictable behaviour. It's not that one can see them before it's too late, there are no charts for their flying routes, and the altitude is also unpredicteble. for exeple Swans are found to travel between Iceland and continental Europe at altitudes up to 27000 feet. Goose flocks were find even higher, and so far the record of altitude goes to Ruppell's griffon, at 37900 ft - and that altitude measurement is very accurate, because at that altitude it was sucked into jet engine of a liner at 29 of November 1975.
If one will take time to dig into bird strike reports - will find that in case of crew member wearing helmet, and his visor down, was always able to control the aircraft. But in cases of not having visors down, there were some cases of knockouts, and blindness (both to windshield and bird parts hitting eyes). But no deaths... and this is different when we look at statistics involved bird strikes and pilot not having any protection. I didn't found a report that would say the pilot whose windshield was hit by a bird of enough energy to shatter it - was able to still fly the machine.
I'm not keen of taking such risk, and I wouldn't trust someone who's willing too.