I am not a shill and I have a Tap because a friend of my had an Echo and I loved it, mostly b/c I use Prime Music a ton and my young kids can easily interact w/the device to play what they want. Several of my friends have purchased the devices after using mine.
I mean, popular? No, not nearly as much as Amazon may like you to believe; however, they are pretty great devices for what they are and I think the recognition software is world's better than Siri (which, IMO, is completely and utterly useless and I never use on my Mac or phone).
By all means, be skeptical, however it doesn't mean they're not being used by people and they're not any good.