Is a conversion a lesser beast? (a long poorly focused ramble here)

I've always wondered why folk prefer a track frame for riding london streets.

I don't know about "prefer" but an ordinary track frame can be a fast handling and very efficient town bike.

obviously, I wouldn't recommend a modern alloy track bike as a long distance machine, for putting the miles in in the cuntryside. But it has been done...I know some men who ride silly track bikes on long hauls then run a mile on it.

No point in being needlessly battered by a stiff bike if you can't/dont want to handle it on the road, but also no fun steering a barge-like cruiser round like a doughnut in granny's greenhouse.