Having the thumbnails show in the email itself means people don't have to break their stride to know whether the photos are ones they're interested in. I keep in touch with a lot of family and old friends using the same email. Different people care about different photos.
Am I the only one who hates corporate email so much? Even for companies I like, I hate receiving email from them.
I'd love to have a no-email policy. Email scams could then be avoided, unless people respond to phishing despite a declaration, "we will never email you".