I remember when I was at uni we used to see people going "power walking" and wondering what their rush was and why they couldn't just enjoy their walk. Didn't find out til decades later that you're "supposed" to travel at enough of a clip to elevate heartrate.

I guess a lot of people if they're utilising their gym memberships or walking every day or whatever might be staying in comfortable ranges where things are going to progress extremely slowly (assuming that's kept up regularly).