Speaking from my experience in Australia, Prime is quite good for ad-hoc ordering.

For AUD6.99 a month I can order something that will usually turn up tomorrow morning, meaning that if I need a light bulb or a dishcloth or weed killer it’s just a 30 second search with the app on my phone and I can get on with my day.

Compare that to:

eBay - free shipping, a week or so, “express” , 3 days and AUD12-18 per purchase.

Small online retailers - generally no free shipping, usually an Australia Post option at AUD12 or so that takes about 4-5 days, “express” via various couriers that takes that to 2-3 days for AUD18-30.

Large retailers - a week or more for delivery, AUD10-40 depending on size.

Me going down the shops and buying it myself - AUD60/hour labour and consumables, 30 minutes to an hour depending on what I’m buying and where from, AUD30-60.

Say what you want about their treatment of workers, from a consumer point of view Amazon’s warehousing and delivery logistics are pretty effective.

Added edit: I don’t live in a “rural” area (of which there are plenty in Australia), but I’ve sent stuff there using Prime and even then it’s only an extra day or two on top.

Oh and there’s Prime Video, and I’ve watched a few shows on it but it’s not something that I particularly need or desire.

And sure , I could do without Prime. Just like I could do without brunch at a cafe once a week, or I could do without Netflix. But it provides a service that is generally cheaper and more convenient than the other options I have so… I’ll just continue to use it until it doesn’t.