DVD burner using my Hard Disk

I have a DVD Drive (E: ) and also a DVD Burner drive (F: ) on
my computer.

All the software I use seem to need to burn the DVD in drive E: to my hard drive first and then burn it from there to my blank DVD in drive F:

My question is why does it need to burn to hard disk first?
Is there any software that buffers first into RAM and burns while buffering?

Basically I want to burn directly from Drive E: to Drive F:.

This is partly dependent on the speed of the drives. Does the dvd-rom drive read at the same speed or slower than the dvd-r/rw can write? If the two speeds are too close the program may consider it too close a call and prefer to rely on the hard disk. There’s also other factors to consider, such as processor power, memory, background tasks, etc. If you do on-the-fly recording, a tiny slip during the read/write operation can ruin the whole dvd-r/rw.
Here’s an idea though: if you can set the write speed to be low enough (half to 3/4 of the dvd-rom reading speed?) perhaps the software will allow you to do on-the-fly recording?