Isn't part of the point of the prefix to avoid collisions with sounds that are part of everyday speech not intended for the assistant? "Alexa" becomes problematic when Echo is used in a office/home in which someone is named Alexa --
among the top 100 most popular female baby names since 1995 [0] -- which is why the wakeup word can be changed to "Echo" or "Amazon" or "Computer".
But the sound of the wake word, whether it's just "Alexa" or "Hey Siri" vs "Siri, doesn't seem to deal with the main issue of your complaint, which to me is how limited "conversation" is with the assistant.
If you ask Alexa for the weather, you'll still have to say her name for any followup questions within that immediate context, i.e. "Alexa, what's the weather today? Alexa, what's the weather this weekend?".
Though there are a few functional exceptions in which Alexa will prompt you for additional information without needing to be re-awakened, e.g.
You: "Alexa, set my alarm for 6 'o clock"
Alexa: "Is that 6 'o clock in the morning, or in the evening?"
I always felt that Siri was named with the intent that it could be used as a wake word (so you could say "Siri what's the weather today?") because Siri itself is a rare given name and [si ri] are sounds rarely said at the beginning of a sentence.
And then at some point Apple realized they had to make a longer wake word to cut down the number of false positives ("Siri" -> "Hey Siri", from 2 syllables to 3).
Google probably went through the same process ("Google" -> "Okay Google", from 2 syllables to 4).
Amazon probably deliberately chose a 3 syllable name with "Alexa" for the same reason.
I can imagine future improvements where we can have the originally imagined wake words "Siri", "Google" and "Alexa", and at that point I would be most happy with "Siri" because it would be short and not-corporate.
I have my Echo set to use "computer" as the wake word because it's just way more fun that way. But, of course, "computer" is a pretty common word these days. It hasn't yet been annoying enough for me to change it.
But the sound of the wake word, whether it's just "Alexa" or "Hey Siri" vs "Siri, doesn't seem to deal with the main issue of your complaint, which to me is how limited "conversation" is with the assistant.
If you ask Alexa for the weather, you'll still have to say her name for any followup questions within that immediate context, i.e. "Alexa, what's the weather today? Alexa, what's the weather this weekend?".
Though there are a few functional exceptions in which Alexa will prompt you for additional information without needing to be re-awakened, e.g.
You: "Alexa, set my alarm for 6 'o clock"
Alexa: "Is that 6 'o clock in the morning, or in the evening?"
[0] https://www.ssa.gov/OACT/babynames/index.html