The proportion paying for points would probably be under 10% of that population. Indeed, the routine advice on forums is that paying for points is bad value except for when needed to top up a specific redemption that is available to book right now.
But the 'advantage of the passenger' is an interesting point. If you are willing to pay $3,000 for business class return and you get a business class return for $3,000 after navigating all the traps of points redemptions, I would argue you have not really gained an advantage. You've traded cash for what you consider to be fair value for the seat, and had to navigate a whole lot of difficulty along the way.
You only get an advantage if you get it for below fair value. For example, if you think the fair value for a business class return ticket is $3,000 and you get it for $1,000 (by credit card churning) and navigating all the traps of points redemptions, then you have gained an advantage. You've saved $2,000 by being willing to navigate the difficulty of reward bookings.