The Echo (Dot) is popular because it (often) works from across the room. You can just place it almost anywhere, and it’ll talk to you. With the Echo Show, you’re back to a user<->display interface. You’ll have to walk over to it. You’ll have to place it more carefully in the room. And that even though it’s much bigger and bulkier than the Echo (Dot). At the same time, unlike a tablet it needs a power outlet.
A screen obviously has advantages. But I’m unconvinced that the use case for the Echo Show is large enough – to me it seems more reasonable to better integrate Siri into the Kindle tablets and maybe equip them with a dock. And personally, I still believe there’s a bright future for smart wearables. The problem with the Apple Watch is that Siri is too slow and too limited. If it were better, you had the screen wherever you currently are.
Also, Alexa is still extremely limited. She’s a generation ahead of Siri IMO, but you can still tell there’s not a single shred of AI in her; it’s all just an advanced ELIZA. As such, I’m not sure of the long-term mainstream use. Personally, I only use her for controlling my lights. Sometimes I ask her to play music, but even that is far too limiting for my taste. At first everybody is excited by her and using all sorts of features – but the question is, how are people using Alexa after even half a year? To me this turns out almost exactly like Siri: as a great but niche interface for some features. I’m willing to spend €60 per device, not not over €200.