Eh? No one said they didn't have any money.
DH and I both work. We have three DC. We want them to have variety of experiences. So we go to the beach, to lakes, to cities, and to theme parks. If we can go to theme parks for half the price, using vouchers, then we will because it means we can then spend the money we have saved on something else.
It's what normal families who have to budget do.
Some families can't afford theme parks etc, even with vouchers. Some don't need to think about vouchers, and can afford to pay full price without noticing an extra £100 here or there.
But most people using MN can afford the odd trip to a theme park, and may well use vouchers. But they also hope to have a nice, clean, entertaining day out, and can feel ripped of if they haven't used vouchers and been provided with less than sparkling service.
The entrance fee to Legoland for DH, I and three DC, would be a large chunk of our family budget, and we earn above average between us.