When I got my first RaspberryPi, I was happy plugging stuff into the pins until I realised that the dust is starting to build up, so then I thought "I need a case", so I got a case.
Then I saw, hmmm, I need to open the lid of the case to plug things in. Hmm, I have lots of cables plugged into stuff and my fingers are not that small to get all the way down there and around the existing cables, even with a case flip lid, the cables got in the road.
I wonder if Smalldevices have a header that I didn't see when I was looking for cases. Wait, what's this, a header that lifts the pins higher, thats the very thing.
I ordered, it arrived, I plugged it, and happy happy days.
So, yes, you do need a header if you have the situation of lots of cables and they are all the way down there....