Because if you leave it at that, it's magical.
We all know that it is certainly not magical. I've tried several brands of SD cards and it's not like i could make DOS recognizing them immediately. First thing i formatted the cards in FAT file system normally on Windows. Most cards would be recognized by DOS to be re-formatted and DOS installation could follow normally. Other brands (like Kingston cards for instance) wouln't work, DOS didn't see any Hard Drive.
I was not interested in finding if the underlying cause for some cards not to work was either the BIOS, the SD Card to IDE controller, the differences in SD cards brands, the software i was using to format, the tooth fairy etc... At that moment i just wanted to make them work. So i remembered about trying GParted which was installed in my Linux Mint partition. So i formatted and partitioned (if bigger than 2GB) cards that were not being recognized by DOS as a hard-drive. What happened is that every single card that wasn't working started to be recognized by DOS as a Hard Drive. I actually went to trouble to format again one of those in Windows again which made the card not to be recognized by DOS again.
Again, i'm sure it's not magical, but i assumed GParted formatted the card in a way Windows and even FDISK DOS tool (i tried it also) couldn't. Whether it was something to do with creating a proper MBR, FAT properties, Data Cluster... i don't care... The cards started working and that's enough for me, so i preferred not to speculate about it because i feel i lack the proper knowledge about the subject and doing so might have lead me to jump conclusions that could be incorrect.
I never speculated about the technical reasons GParted worked for me. If i did, and assuming the possibility i could be wrong, i would be spreading misinformation.
Try and find the underlying cause.
You're not the boss of me.