This is why i say its up to the user,i got something sticky on my zoom the first day out with my D70 and it never completely cleaned off.
Look on ebay and see how much the value drops with a scratched front element,yes cheap filters are a no but some cost twice what each element in the lens costs,but we always get the emotive shout from some one about putting cheap glass in front of an expensive lens,i had a mate that boasted he never used condoms,he ended up at the clinic,its a lottery.
I'll never know how I got the scratch on my 35mm but it made me realize that it's plain silly to pay 2k for some lenses and then cheapen out on a 100$ filter protecting them. I'm also carefully stuffing my D810 in a bag and not throwing it in the trunk like it is.