Originally Posted by 531Aussie

because there's no derailleur (with springs in it) to control the chain tension, you've gotta pull and hold the wheel back along the drops while you tighten the nuts to get the correct tension.

Also, it's common for trackies to regularly change the cog, which obviously alters the chain tension, so you can't really choose one gear, then "set and forget". So, even if you only ever used one cog, it would be virtually impossible to get the chain lengeth exactly right for a vertical dropout.

I haven't ridden a track bike for a long time, but, because there's no derailleur constantly moving on the springs to control perfection tension, track bikes are nowhere near as smooth as a road bike.