I don't want that to happen because the price variation in toilet paper is huge based on deals and offers available, and Amazon is rarely the cheapest provider these days, so it's actually worth me spending a few minutes on it to save some money.
The reason Alexa exists is to sell you Amazon's prices, not necessarily a good deal.
Also, I think I'd rather just add stuff to my shopping list so that I can at a later time order everything together, rather than have multiple deliveries.
The sort of consumables I might order on Amazon on a regular basis--like those that the Amazon Dash buttons were intended to address--can vary a fair bit in price and quantity. I'm not going to have Amazon just ship whatever.
And it's not even a very frequent thing. Mostly, every few months, I look through what consumables need replenishing and I fill up the car with plus-size packages from Walmart.
The reason Alexa exists is to sell you Amazon's prices, not necessarily a good deal.