Americans wouldn't necessarily know that however especially if they are new immigrants.
That's why they are putting out these adverts to show how the NHS works. GPs will keep pushing for a charge for a visit otherwise if the time wasters keep taking up their time: just as other countries with a national health service, already charge for a GP visit. NHS GPs and dentists are self employed and have contracts with the NHS: they need to make a living too.
Our first instinct is to go to the doctor. In a lot of cases we could get same day appointments if you called early in the morning and you could always go to an urgent care clinic or minute clinic.
We have non-NHS GPs, hosptials etc too, like the US system, where insurance is used. Many employees will give insurance to their employees. Other people might buy their own medical insurance, or pay when they want they want treatment.
The days of the same day appointment for the NHS GPs are becoming too hard to get. If the time wasters can be stopped, then those appointments can go to those who really need to see a GP.