Because we’re constantly lied to in the name of market capitalism, and unless you have at least a passing familiarity with the subject at hand, it’s sometimes hard to decipher when you’re being told a lie and when it’s the truth.
We’re told that Crest is the “best” anti-cavity toothpaste without being told that “best” is a specific marketing term that means “no better or worse than any other parity product in its category,” and that if you really want the “best” toothpaste, look for the one saying it’s “better,” because that’s an actual statement of comparison that will get them in trouble if it’s a lie.
We’re told that Cascade dish powder leaves dishes “virtually spotless,” but are not told that in marketing speak, that means “not spotless.” News anchors will tell us that “some people say (controversial statement)” which really means “I said that to generate a story, I’m ‘some people,’ and therefore it’s technically true.”
The list goes on, virtually up to 99.9% of forever, guaranteed (terms and conditions apply).
Specifically regarding oil changes, just about every shop out there still puts 3 months/3000 mile intervals on that oil change sticker they afix to your windshield, even though no manufacturer except maybe Lada recommends such a short interval anymore.
So it’s not terribly surprising when someone sees “every 6 months” and wonders “huh, do I really need to do that, or is the company covering its butt against warranty claims by artificially shortening the maintenance interval?”