Mostly just doing it for fun. Some people try bases where they mostly use bots, or mostly use trains, etc. I've just taking a liking to burner inserters of late, and trying to see if I can come up with some "good" furnace layouts, or "good" science builds using only burners has been a fun experience ...

Mixing the coal and ore on the same belt meant ....
Why your not simplifying matter by using a electric furnace?

I would still need the coal to feed the burner inserter itself. Changing the furnace type doesn't fully address the problem; would reduce the required actions of the loading inserters ...

Mixing the coal and ore on the same belt meant that the belt ran down too fast: burner inserters have a hard time grabbing from red belts, spending a lot of their time trying to grab an item as it goes past, and a yellow belt with half ore and half coal can only sustain ~10 furnaces (if I recall ...

I've been playing with burner inserters recently. Trying to work around the coal requirement has been tricky, but I worked out a decent smelting setup. One input inserter couldn't keep up with the furnace's demands for both ore and coal, and two inserters meant that the belt couldn't keep up. I don ...