Simple things like:
"Remind me to X tomorrow at 9am" "Add Y to the shopping list" "Remind me to do Z when I get home"
This is the only way I do reminders now and it's great. It's especially useful while driving, or when I'm in bed nearly asleep and remember something, I can just tell Siri without having to get up and use my phone.
And as far as smart home controls, being able to say "Siri, turn all the lights on" or "Siri, turn the heater on" without having to stop what I'm doing and walk around the house flicking switches is really nice.
Assistants provide a very noticeable QoL improvement for me in many aspects. I think that's more than most other products on the market can say. And that's not even touching on the lives saved from not having to use your phone while driving.