You're right, we disagree.
The average age of an Airbnb user may be 25 but many hosts find that they host mainly older people. And does 'use'; include hosts? And children who travel with their parents?
I will not 'also find' that Generation Y is more accustomed to apps and the internet. Most people of 55+ have been using the internet since today's 25 year olds were toddlers. Many have been using apps since those twenty five years olds were ten years old and few parents in those days would let their kids use iPhones.
You are also incorrect in saying that Airbnb is a cheaper option. It might be 'considered' a cheaper option but in many cases it isn't, especially when Airbnb and cleaning fees are taken into account. Many, many listings are more expensive than cheap hotels.
Over 55s are also often more adventurous when it comes to different types of accommodation and there have always been cheap STRs for younger people - hostels and so on.