I have an exterior front door that needs replacing.

The former owner put a kick plate on a steel door. That means rust.

I need to replace the door, but frankly I do not want to, nor do I feel it
is necessary to shell out about 2.5K to replace a door and two sidelights.

It seems to me that an 80x36 door is an 80x36 door, and I should be able to
go get one.

Is it a scam that the local hardware stores and local contracters are trying
to tell me that i need to replace the entire unit?

Seems like a steel door is about $140, but perhaps there is not enough
margin on that to make it worth while, so they push replacing the entire
unit.

Can someone shed some light on this?

NOTE: House is 21yrs old.

If I do need to replace the entire unit, why isn't a door a door?

Thanks,

Bob