If you can’t afford some extra $500/mo charge (be it some emergency repairs on your roof or a new heater, etc), then you have no business buying a house when expenses can crop up at literally at time.
For those who can look past what is happening today, they can see that the temporary hit of $500/mo for 5 years can result in potential savings of hundreds of dollars each month for 20 or 30+ years.
The fact that people have to even be explained this concept probably means they have no business hanging around in a home improvement community. Because you know, some of us like to improve our homes and not live in squalor, and things cost money. That sounds like it is a foreign concept to some in here.