Do these asphalt shingles really last 25 years, as claimed?

When asking roofers about fixing my roof, they tend to say “nah it’s not worth it. We do new roofs only”, then give me a quote of “specially treated asphalt roofs” that’s expected to “last 25 years” because “it’s resistant to moss, weather, fire, and basically everything”.

I’m a complete dummy in this area but it sounds highly suspicious to me. I’ve just never seen any roof that’s installed more than 20 years ago be in excellent condition. More often than not, I see roofs of new constructions within the past 10 years already in bad condition - discoloration, moss growth, fracture.

Experts- Does the “super enduring asphalt roof” really exist, or is it total bs? And also how do the roofing companies “guarantee” it to last that long? I don’t see many roofing companies stay in business for 25 years either.