Indeed, and "perfect accent" varies from device to device. My wife and I are both from the Atlanta, Georgia area, yet we have distinctive accents; hers is much more "Southern" than mine as I grew up in several different states across the Southeast and Southwest, whereas she lived in the same house from birth to college, then moved back after graduating.
We've found that her Nexus 6 understands me better than her even though she talks to it far more often than I do, and the reverse is true for our Shield TV despite it using the same backend as the phone. She has to try two or three times to get her phone to understand a command, where I can get it right the first time. On the Shield, I will tell YouTube to look for "funny cat videos" and I get "funny hat videos" every damn time, while she gets cats.
So, bachelor Silicon Valley engineers.
I don't know about Google Home or Siri, but my Alexa easily handles my broad Norwegian accent the vast majority of the time.
There are a few things (e.g. weird album titles) that are more likely to cause problems, but in my experience the things that it has problems with are rarely accent related as when something is problematic my son who does not have a comparable accent runs into the same misrecognition.
(EDIT: I have no doubt that there are accents it will have problems with - my point is that you certainly don't need to have perfect pronunciation for this any more)
> While I could just have pressed the play button on my Apple TV remote and be done with it (no fiddling with a phone necessary).
That requires finding the remote first. You may be organized enough for that never to be an issue. I've given up on the normal remote and rely exclusively on apps now, but that also involves grabbing my phone or tablet and a couple extra steps.
> (4) Voice assistants are unusable in most environments where there are other people.
That's fine. They don't need to be usable everywhere. I have no interest in using one on my phone in public for example. But I like having one in my living room, and I rarely have enough people around that it's a problem. In my experience with it so far, people have already learned to hush down automatically when they hear you give the keyword (but I do agree that won't work with a lot of people present - it works with a few people around).
My TV is so old the remote is still wired to it. Finding the remote is never an issue.
Reality: if you have a slightly non-standard accent, you will be shouting at your device five times before anything happens. While I could just have pressed the play button on my Apple TV remote and be done with it (no fiddling with a phone necessary).
Then there are all kinds of cultural realities that are apparently not considered in Silicon Valley. My favorite five pet peeves:
(1) Our family name is 'de Kok'. Very often these assistants totally mess up when I ask e.g. to call family (either they start complaining about dirty language or literally search for 'cock').
(2) We are a multilingual family, languages used in our household are German, Dutch, and sometimes English. None of these voice assistants work with multiple languages. So, the only alternative is to choose one language and stick with it. Unfortunately, if you choose English you are having a hard time navigating in Germany, looking up a German TV program, or calling a Dutch or German friend. If you set the language to German, you forgo looking up shows on Netflix by their English titles reliably.
(3) Usability goes down the drain once you have kids. Voice assistants typically do not work well when multiple people are speaking at the same time. If you are lucky, they are just confused, if you are unlucky they start doing whatever they infer from a semi-random mix of words. You cannot tell your three year old to be quiet, because mom or dad has to tell Siri what to do. (I use Siri sometimes, and our daughter currently likes to scream 'hey siri' repeatedly when I use Siri.)
(4) Voice assistants are unusable in most environments where there are other people.
(5) Voice assistants, especially in-house voice assistants are a potential privacy violation. So, you have to ask people that visit you if they are OK with your conversations being recorded (accidentally or intentionally) and switch off the device if they do mind the latent spying.
tl;dr: voice assistants only work well in monolingual families where all of the family members have a perfect accent and where none of your acquaintances mind the privacy violations.
Edit: added some more annoyances.
Edit 2: heavy downvoting :/. Please explain why!