Welcome to the internet... I personally consider tyres a consumable but I'm happy if you're happy, so carry on.
I have the original Eagle GT tires from my 1980 Corvette with about 1/3 tread left. Are they on the car? Oh hell no! But I keep 'em because they are cool and I could mount them on another set of wheels and swap them on at a concourse event. It's all good. Another note. Most reputable tire shops in Colorado will not do any work on a tire that is 10 years or older. No flat repair, no spin balance . . . you get the picture.
I will now eat a huge slice of humble pie... A Peugeot 205 sold at a UK auction last weekend for over GBP 30,000 (US$ 40,000+). A key statement in the report below is: "Its also almost exactly how Peugeot intended, with only a tasteful stainless steel exhaust and Cobra alarm being added since leaving the production line. Talking of which, this little pug still sits on the tyres it was sold on sketchy, but just what the collectors are looking for." https://revmatch.me/2016/08/01/timewarp-peugeot-205-gti/