Why would the average person give a fuck about their privacy? Most people have nothing to hide, and unless they are a fanatic or a hobbyist, they could not care less who reads their stuff.
I agree with you. The average person probably doesn't care, but that doesn't mean he/she shouldn't care. Privacy is important to everyone, even if you're one of those persons who mistakenly believes that you have nothing to hide.
Divorces, custody disputes, false accusations, lovers' quarrels, medical sexual history, medical history, dating, underage alcohol consumption/sexting/sex, stalkers, job interviews, job-related credit checks and/or background checks (depending on the type of job and your local laws), salary negotiations, career promotions, college/school applications, car accidents, car insurance penalties, red-lining, profiling, red light cameras, speed cameras, identity thefts, arbitrary tax laws, IRS audits/penalties (if you don't live in the US, replace IRS with the relevant tax/customs authorities), collection agencies, filesharing, porn, sexual orientation, tethering, rooting your own device, netflix/hulu-specific throttling, recycling fines, arbitrary electricity/water consumption fines/penalties, housing association violations, neighborhood/city zoning/building violations, cigarette smoking violations, dog leash/breed violations, contrived political redistricting, poll tampering, etc.
And it is true, that as individuals, we may not care that much about each particular privacy-related issue, but as a whole and as an aggregate, we should care, because every single one of us is impacted by at least some of these issues and consequences.