Honestly, I used to think the same thing. Unfortunately, it's not that simple. I have 6 cars. 3 are always in the garage when not in use. The other 3 are parked outside. Of those, two are driven regularly and one is parked because it's only used for RallyX. I've never had an issue with the 5 but the RallyX car had a ton of moisture in the oil every time I've changed it at the start of the season after letting it sit outside for 6 months. At first I thought I had a coolant issue but then realized that it was just attracted moisture.

Aside from that, how much are your cars worth to you? "Wasting money" is a questionable statement for such a low cost maintenance item that has a high cost if you have a failure due to that issue.

To each their own. It's the internet and opinions are like a-holes.

I trust what my oil analysis says.

I have a 2004 WRX that sees about 1500 miles/year. My BRZ sees more now at about 4-5k/year.

I used to change it every 6 months, but I've been going about a year. Haven't noticed any difference. It's only 1500 total, but there's a decent amount of idling and cold starting for winter when it's used more when the BRZ gets put away in the garage for 5 months.

Personally, I'd do yearly. It's not that expensive. Get an oil analysis done. My main concern would be water or fuel depending on how it's driven. I do them on the BRZ, but not WRX due to the mileage it sees now.

I change oil and filter once a year, which is less than 3000 kl.
My garage queen only appears for occasional pleasure cruises and a couple track days a summer which include a 400 kl highway round trip.