Being glib aside, there is a vast population of poorer people who either live in countries with unstable banking systems or are just not profitable for banking. These people will get the most value out of bitcoin.
It's like landline telephones. For people with established land line systems, the value of a cellphone isn't that much. For people who've never had a phone, and wont get land line service, a cell phone is amazing!
ACH/Wire transfers are very slow for Americans, and too much inertia makes it seem like they're not going away soon.
I get what you're saying but...this just doesn't make sense. If this was true, how do you explain the now ubiquitous usage of cell phones? Neither I nor any of my (in their 20s) friends have a land line, because we all have cell phones.
Now cellphones are everywhere, but pre-iphone era USA was rather backwards in terms of mobile phone usage. Also, "majority of young people being mobile-only" was an obvious thing in many much poorer places long before USA. None of the people I know in their 30-ies have had a landline for more than 10 years now - as far as I remember this was not the case in USA back in early 2000's.
Btw, why isn't ACH/wire transfers a solution? If done properly (unlike USA), they cost a few cents and can be transmitted in less than an hour (not 24/7 yet, though).