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.