It has nothing to do with browser support, although that has been an issue in the past. It has everything to do with Aunt Millie "feeling secure" when she sees the Verisign Secure Seal moreso than, say, the Godaddy Badge.
Can you back your assertion up with some evidence ?
"Seals" used to be quite popular some years ago (e.g. TrustE seal and the BBB Seal), but they seem to get less press these days, so I wonder how important they are for conversions.
Has Aunt Millie really heard of Verisign ? May actually have heard of GoDaddy though due to the advertising.
Not linkable evidence, no, although Verisign has their own collection of user stories claiming huge conversion increases in their marketing literature.
We have done A/B testing on Verisign seals vs no seals vs generic "Secure Site" seals we created. There is a statistically significant increase in conversions with the Verisign seal vs the other two options.
It's all about the conversion rate, basically.