Well ECC is not the be-all end-all. There are several sources of bit errors. SD-Cards, USB Flash drives, TCP/IP Packets, HDDs, SSDs etc etc. Thats just the 'bits' you have control over. If you're copying data from somewhere else, you have no control over what the other person does to it, etc etc. I wont't produce a thesis here, but you get the idea :)
Hmm, do you happen to know what the actual improvement is, in terms of a reduction in the probability of bit errors? What I'm thinking is.. assuming there are multiple weak links in the chain, strengthening one link, might not really make all that big of a difference. But I agree with the general point you're making - something is better than nothing.